Compounds (R = Sc, Y, GdâLu) - American Chemical Society

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The new RPd compounds (R = Sc, Y, Gd-Lu): formation and stability, crystal structure and antiferromagnetism Alessia Provino, Nediadath Sathyanadhan Sangeetha, Sudesh Kumar Dhar, Volodymyr Smetana, Karl A Gschneidner, Jr., Vitalij K Pecharsky, Pietro Manfrinetti, and Anja-Verena Mudring Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b01045 • Publication Date (Web): 06 Sep 2016 Downloaded from http://pubs.acs.org on September 7, 2016

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Crystal Growth & Design

The new R3Pd5 compounds (R = Sc, Y, Gd-Lu): formation and stability, crystal structure and antiferromagnetism Alessia Provino,*,†,§,‡, Nediadath S. Sangeetha,¥,◊ Sudesh K. Dhar,¥ Volodymyr Smetana,§,⊥ Karl A. Gschneidner Jr.,§,⊥ Vitalij K. Pecharsky,§,⊥ Pietro Manfrinetti,†,§,‡ Anja-Verena Mudring§,⊥ † §

Department of Chemistry, University of Genova, 16146 Genova, Italy

Ames Laboratory, USDOE, Iowa State University, Ames, IA 50011-3020, USA ‡

¥

Institute SPIN-CNR, 16152 Genova, Italy

Department of Condensed Matter Physics & Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India

⊥

Department of Materials Sciences and Engineering, Iowa State University, Ames, IA 50011-2300, USA

ABSTRACT The phases reported in literature as “R2Pd3” (R = rare earth element) have been reinvestigated. The exact stoichiometric composition of this series of compounds, which form for R = Sc, Y, and from Gd to Lu, including Yb, was found to be R3Pd5. All of them crystallize in the orthorhombic Pu3Pd5 structure type (oS32-Cmcm). The crystal structure has been refined from both single crystal (for Tb3Pd5) and powder X-ray diffraction data (for Tb3Pd5, Ho3Pd5 and Tm3Pd5). These compounds represent the first example of a binary phase formed by R and Pd adopting the Pu3Pd5-type featuring two crystallographic non-equivalent sites for the R atoms in the unit cell (the Wyckoff sites 4c and 8e). The variation of the lattice parameters and unit cell volume along the series strictly follows the trend of the lanthanide contraction. An extrapolation of the volume contraction vs. the R3+ ionic radius gives an atomic volume of 29.74 Å3 for Yb in the hypothetical trivalent metallic state (under normal conditions). The formation temperatures and mechanisms, a peritectic reaction, and stability ranges have also been investigated. It turns out that Gd3Pd5 is a high temperature phase; it was not possible to quench this compound, as a metastable phase, at room temperature, to be measured. In the light of our results, most of the R-Pd phase diagrams require to be revised. The magnetization, heat capacity and electrical resistivity have been measured for Tb3Pd5, Dy3Pd5, Ho3Pd5 and Er3Pd5. They order antiferromagnetically at low temperatures, each undergoing two transitions, TN1 and TN2 (with TN1 going from 13.5 K to 5.1 K and TN2 going from 6.5 K to 3.6 1 Environment ACS Paragon Plus


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K, respectively for Tb and Ho compounds). From our data we cannot distinguish whether the two rare earth sublattices sequentially order magnetically at TN1 and TN2, respectively, or whether they are simultaneously involved in both transitions. The electronic structure calculations predict antiferromagnetic ordering also for Gd3Pd5. Y3Pd5 is a Pauli-paramagnet. Keywords: R3Pd5 intermetallic compounds; Crystal structure; Formation temperatures; Antiferromagnetic ordering; Physical properties.

* Corresponding author: Alessia Provino (e-mail: [email protected]) ◊ Current address: Ames Laboratory, Iowa State University, Ames, IA 50011-3020, USA.

1. INTRODUCTION The R-Pd (R = rare earth) binary systems have been investigated for many years.1-5 However, only some phase diagrams have been determined experimentally in full, i.e. the diagrams of the Y-Pd, Sm-Pd, Gd-Pd, Dy-Pd, Ho-Pd and Er-Pd, which were investigated by Loebich et al.,1 and those of Eu-Pd6 and Yb-Pd7 which were studied by Iandelli and Palenzona. The remaining R-Pd phase diagrams reported in literature are incomplete, experimental data are only available for a limited composition range (Sc-Pd, Ce-Pd, Pr-Pd, Nd-Pd, and Lu-Pd).1-5 The liquidus curves are often either not well defined or are lacking, while binary phases are reported with uncertainty. Some of the experimentally investigated R-Pd phase diagrams have been more recently re-assessed computationally by using the CALPHAD technique8 (i.e. those of the Eu-Pd,9 Gd-Pd,10 Dy-Pd,11 Er-Pd12 and Y-Pd13). The Tb-Pd system has been predicted based on an interpolation of the systematic trend in R-Pd alloying behavior.14 The La-Pd and Tm-Pd phase diagrams have not been investigated yet, neither experimentally nor theoretically;2 only the existence of some binary phases has been reported. A collection of the R-Pd binary compounds reported in literature, with their given stoichiometric composition, is listed in Table 1. Among the existing binary phases, evidence for formation of two compounds with apparent stoichiometries “R2Pd3” and “RPd2” is reported for the majority of the rare earth elements, though neither the crystal structure nor the exact compositions of both these phases have been ever determined. The “R2Pd3” compounds have been reported for R = Y, Pr, Sm, Gd, Dy, Ho, Er, Lu and Yb (the last one has been described as YbPd1.677). All of them are reported to be dimorphic, with high and low temperature forms, except for Gd, for which only the high temperature phase is detected.1,10 A recent investigation of the phase equilibria in the Lu-Pd binary system15 revealed a phase with composition Lu2Pd3, crystallizing in a monoclinic unit cell with lattice parameters a = 7.78 Å, b = 8.90 Å, c = 12.21 Å, β = 117º (space group C2/m), confirming an earlier report.16 2 Environment ACS Paragon Plus

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However, to date, the compositional and structural identity of the compounds with nominal composition “R2Pd3” and “RPd2” have not been investigated in detail; this triggered our interest for a systematic study of these phases. In this work we report on the formation, crystal structure and exact composition of the phases earlier reported in the literature as “R2Pd3”. We found that the actual stoichiometric composition of the “R2Pd3” phases (or “RPd1.67” for Yb7) is R3Pd5. Our investigations revealed that the R3Pd5 compounds crystallize in the orthorhombic Pu3Pd5 prototype [oS32, Cmcm (No. 63)].17 The Pu3Pd5 structure type is adopted by a number of binary intermetallics. Most of them are formed between a divalent metal, or a rare earth element, with a p-block element: Ca,18 Sr,18,19 Ba,20 Eu,21,22 Yb23,24 with Tl, Ge, Sn, Pb, and La,25-27 Ce,28,29 Pr,30,31 Nd,27,32 Sm, Gd, Tb, Dy, Ho, Er, Y,27 Lu33 with In, Tl and Sn. A few examples are also found for Zr (viz. Zr3Ga534 and Zr3Rh535) and actinide intermetallics (Th3In5,36 Th3Tl5,37 U3Ga538). The only R-Pd compound with a composition of R3Pd5 that has been previously reported in literature is Ce3Pd5, which, however, crystallizes in the hexagonal Th3Pd5-type structure [hP8, P−62m (No. 189)].39 We have also probed in detail the magnetic properties of the R3Pd5 (R = Y, Tb, Dy, Ho and Er) compounds by magnetization, heat capacity and electrical resistivity measurements, which reveal two antiferromagnetic transitions for compounds formed by magnetic lanthanides. Preliminary results on the magnetic properties of some R3Pd5 compounds have been recently reported by us.40-42

2. EXPERIMENTAL SECTION 2.1. Synthesis. Alloys (total mass of 1.5-2.5 g), with nominal compositions R:Pd as 2:3 and 3:5, were prepared by arc-melting the high purity commercial metals (99.9 wt.% purity for all R, and 99.99 wt.% purity for Pd), under a Zr-gettered Ar atmosphere. In the case of Yb alloys an excess of 3 wt.% of Yb was added to compensate for the weight loss due to volatilization of Yb. In order to ensure the homogenization of the samples, the ingots were re-melted at least three times after turning the button upside-down. Total weight losses were below 0.5 wt.%, except for Yb, where the weight loss was about 2.5 wt.%. The ingots were then placed in an outgassed Ta tube, closed under vacuum in silica ampoules and annealed at 1000-1100°C for 7-12 days in a resistance furnace. Finally the alloys were removed from the furnace and air cooled to room temperature. For Gd3Pd5 several samples were prepared and heat treated in different ways, including quenching (Q). The final buttons had a steel-like color and were generally hard and brittle; the powders are slightly air sensitive.

2.2. Phase analysis. The samples were characterized by optical and scanning electron microscopies (OM and SEM), the latter equipped with electron microprobe (EDX) for semi

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quantitative elemental analysis. EDX analyses were performed on at least four sample points (or areas) to identify the phase composition (counting time of 60 sec). Impurities of R3Pd4 compounds present in these samples were used as a standard; the precision of the measurements was estimated to within 0.5 at.%. Microphotographs of the samples were taken both using backscattered and secondary electrons. Structural characterization was carried out by X-ray powder diffraction (XRD) using both a Guinier camera [Cu Kα1 radiation; Si as an internal standard, a = 5.4308(1) Å] and a Philips diffractometer (Cu Kα radiation) for data collection (2θ range of 12°-102°, in steps of 0.02° and a counting time of 28-30 sec/step). The Guinier X-ray diffraction powder patterns were indexed by the help of LAZY PULVERIX43 and accurate lattice parameters were obtained by a least-squares program. In case of the terbium compound, single crystals of sufficient quality for single crystal Xray structure analysis could be obtained. Single crystals of Tb3Pd5 were selected from a DTA (differential thermal analysis) sample after annealing, fixed on glass fibers and mounted on a Bruker APEX CCD diffractometer (Bruker Inc, Madison, USA). Sets of single crystal X-ray diffraction data were collected at 293 K using Mo Kα radiation in φ- and ω-scan modes. Full measurement of 900 frames with acquisition time of 10 sec were performed to obtain raw intensity data. The integration process was performed with the aid of the SAINT program of the SMART software package.44 Empirical absorption correction45 was performed with the SADABS program.46 The SHELXTL47 suite has been applied for the final structure solution and refinement. Details of the structural refinement and atomic parameters are listed in Tables 4 and 5, respectively. Further details of the crystal structure investigations are available from the Fachinformationszentrum Karlsruhe

(FIZ

Karlsruhe),

D-76344

Eggenstein-Leopoldshafen,

Germany

(e-mail:

[email protected]) on quoting the depository numbers CSD-431565. A full-profile Rietveld refinement was performed using the FULLPROF program48 to refine the crystal structure of the Tb, Ho and Tm compounds.

2.3. Differential thermal analysis (DTA). Differential thermal analysis (DTA) was performed for most compounds on a portion of 0.7-0.9 g of the alloy either as cast or annealed. Each sample was enclosed in an out-gassed Mo crucible under Ar flux and then transferred to the DTA equipment (Netzsch 404 thermal analyzer). Thermal cycles were generally carried out with rates of 20°C/min on heating and 10°C/min (or 5°C/min) on cooling: the accuracy in the temperature measurements was ± 5°C.

2.4. Physical property measurements. The magnetization data, M, were collected using a Magnetic Properties Measurement System (MPMS) and a vibrating sample magnetometer (VSM) (both from Quantum Design, Inc., USA). The speciﬁc heat, CP(T), was measured by relaxation method using the heat capacity option of a commercial Physical Property Measurement System


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(PPMS, Quantum Design). The resistivity, ρ(T), was measured between 2 and 300 K by a standard four-probe technique using the AC transport option of a PPMS.

2.5. Computational details. Density functional theory (DFT)-based band structure calculations on Y3Pd5 and Gd3Pd5 were performed using the projector-augmented wave (PAW) method of Blöchl49 as implanted in the Vienna ab initio Simulation Package (VASP).50-54 A Hubbard U correctional parameter was applied to account for the strong correlations within the localized Gd-4f states. The energy cutoffs of the plane wave basis sets were set to 500 eV, while the first Brillouin zones were sampled by starting meshes of 4 × 4 × 4 to 7 × 7 × 7 k-points for reciprocal space integrations. Full structural optimizations were performed until the energy differences between two iterative steps fell below 0.01 meV. A lower symmetrical model has been applied to Gd3Pd5 to allow for the possibility of antiferromagnetic ordering within the given unit cell.

3. RESULTS AND DISCUSSION 3.1. Formation and crystal structure of the R3Pd5 compounds. Our detailed investigation showed that the actual chemical composition of the unknown phases, previously reported as “R2Pd3”, corresponds to R3Pd5. First hints for the true crystal structure of this new phase were obtained by indexing the Guinier X-ray diffraction powder patterns of two trial samples with nominal compositions “Y2Pd3” and “Ho2Pd3”, after subtracting the reflections of the known R3Pd4 phase (Pu3Pd4-type). An example of a SEM photo, illustrating the microstructure of a sample with starting composition “Ho2Pd3”, is shown in Figure 1. The resulting alloy is clearly biphasic, containing primary crystals of Ho3Pd4 in a dendritic form (light-gray phase) in a matrix of Ho3Pd5 (dark-gray phase). Our work reveals the R3Pd5 phases to crystallize in the orthorhombic Pu3Pd5type. These phases represent the first example of a binary intermetallic compound formed by a rare earth element with a transition metal adopting the Pu3Pd5 prototype [oS32, Cmcm (No. 63)].17 The compounds R3Pd5 form by a peritectic reaction at a temperature lower than the formation temperature of the known, congruently melting, R3Pd4 phases. It is therefore very difficult to get single-phase samples of R3Pd5 even after a proper annealing. The formation of the R3Pd5 compounds was confirmed for the heavy lanthanides from Gd to Lu including Yb, and for Sc and Y. Gd3Pd5 is a high temperature phase, observed only in as-cast alloys; despite the fact that it was detected as the main phase in arc-melted samples, it was no longer present after annealing and quenching (see following paragraph). A sample with nominal composition ‘Nd3Pd5’ was also synthesized; however, in this case the 3:5 phase was not present either in the as cast or in the annealed form (820°C, 6 days).



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The lattice parameters (a, b, c), along with the observed unit cell volume (Vobs) and the volume contraction (∆V %) {with ∆V % defined as ∆V = [(Vcalc – Vobs)/Vcalc] × 100, where Vcalc is the cell volume calculated from the individual atomic volumes55 and Vobs is the experimentally observed cell volume} for all of the R3Pd5 compounds are collected in Table 2. The trends of the lattice parameters and unit cell volume, as a function of the R3+ ionic radius,56 are shown in Figures 2 and 3, respectively. The lattice parameters linearly decrease from Gd3Pd5 to Lu3Pd5, including Y3Pd5, following well the lanthanide contraction. The resulting trend of the unit cell volume is also linear, reflecting the variation of the lattice parameters. The data points for Yb3Pd5 lie well on the trend of the other trivalent R indicating a formal trivalent oxidation state of Yb in Yb3Pd5. Yb, along with Eu and Sm, is a rare earth element that shows a strong tendency to adopt the divalent oxidation state. However, a trivalent state for Yb is often observed where the electronegativity of the partner element is higher than ≈ 1.90,57 or in T-rich Yb-T compounds (T = transition metal).6 In this case, the electronegativity of Pd being 2.20, both conditions are met. The obtained lattice parameters for Sc3Pd5 are much lower than those expected from the trend of the other compounds, indicating a stronger than expected volume contraction. A sample prepared with the nominal composition ‘Sc1.5Lu1.5Pd5’ is a nearly single phase with lattice parameters confirming this behavior for the Sc containing phases (Figures 2 and 3). Rietveld refinement of the crystal structure, on the basis of powder X-ray diffraction data, has been performed for Tb3Pd5, Ho3Pd5 and Tm3Pd5 compounds; the results have confirmed their Pu3Pd5-type structures. Figure 4 shows the Rietveld refinement profiles for Tb3Pd5 (4a), Tm3Pd5 (4c) and Ho3Pd5 (4b) samples (the first two being single phase, while the latter contains ≈ 7 wt.% of the Ho3Pd4 compound). The refined atomic coordinates for the Tb, Ho and Tm compounds, along with the refinement data, are collected in Table 3. Full and ordered occupation of all the atomic positions was obtained, with the two Pu sites (4c and 8e) of the prototypic structure being occupied by R atoms. Only for Tb3Pd5 it was possible to obtain single crystals that had sufficient quality for single crystal X-ray structure analysis. Initial indexing revealed an orthorhombic unit cell, confirming the Pu3Pd5 prototype (Tables 4 and 5). The single crystal data agree well and corroborate the results obtained from Rietveld refinement. The interatomic distances for Tb3Pd5 are listed in Table 6; only those corresponding to the first coordination sphere, i.e. those for which dobs/ΣrM ≤ 1.106 (where dobs is the observed interatomic distance and ΣrM is the sum of the two metallic radii58), are reported. Coordination numbers of Tb1 and Tb2 are 13 and 15, respectively, while those of Pd1, Pd2 and Pd3 are 11, 10 and 10, respectively. Figure 5 shows a sketch of the crystal structure for the Tb3Pd5 compound with the highlighted coordination polyhedra for Tb1 (Tb4@Pd9) and Tb2


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(Tb5@Pd10). Projections of the crystal structure along both the b- and the c-axes are depicted in Figure 6. Coordination numbers observed for both Tb and Pd characterize densely packed crystal structures and are typical for intermetallic compounds. Relatively short interatomic distances, which might indicate strong bonding interactions, are observed between the heteroatoms Tb and Pd in the range between 2.786 Å and 3.142 Å (Table 6). The shortest values for homoatomic Tb−Tb interatomic distances are observed between Tb2−Tb2 (3.656Å and 3.702 Å) and Tb1−Tb2 (3.717 Å) and are slightly larger than the diameter of metallic Tb (3.564 Å). Despite the fact that the crystal structure is densely packed, Tb1 and Tb2 atoms in the unit cell are stacked in two distinct layers: Tb1 atoms only lie at z = 1/4 (and z = 3/4), while Tb2 atoms lie at z = 0 (and z = 1/2). The Tb1−Tb2 contacts extend along the c-axis following zig-zag chains parallel to this direction (Figure 7a). The Tb2−Tb2 contacts form a net of irregular hexagons extending in the a-b planes (Figure 7b). Although the Pd−Pd interatomic distances remain almost the same as those in the prototype Pu3Pd5,17 the Tb−Pd distances are relatively shorter than the Pu−Pd ones. This can be explained by a positive volume contraction which takes place in the formation of Tb3Pd5 (∆V = + 8.05 %) and the other R3Pd5 phases (see Table 2) as respect to a high and negative volume contraction associated to the formation of Pu3Pd5 (∆V = − 20.6 %; in this case a volume expansion), in spite of the much smaller atomic volume of Pu (20.00 Å3) with respect to that of Tb (32.13 Å3).55

3.2. Volume contraction and formation temperatures Figure 8a shows the trend of the volume contraction plotted against the R3+ ionic radius. The formation of these compounds is accompanied by a relatively high volume contraction, with ∆V values increasing from about 8.1 % for Tb3Pd5 to 9.8 % for Sc3Pd5, while an anomalously high value of 10.5 % is observed for the Y compound. The values from Tb to Sc (including Sc1.5Lu1.5) can be well fitted by a quadratic function: ∆V =m (R3+)2+ n (R3+) + s (with m = 65.64 Å−2, n = − 129.01 Å−1, s = 71.18). The data point for Yb (8.81 %) in Figure 8a is an interpolated value obtained from the above mathematical function by using the ionic radius for Yb3+ of 0.858 Å.56 This ∆V corresponds to a calculated unit cell volume Vcalc of 650.62 Å3 for Yb3Pd5 and to an atomic volume of 29.74 Å3 for Yb in the hypothetical trivalent metallic state. Such a derived value agrees with the estimated atomic volumes of the trivalent rare earth elements under normal conditions (see Table 9).55 This value can be utilized in future crystal-chemical considerations and calculations concerning Yb intermetallic compounds. In a series of rare earth compounds, with a given chemical composition RxMy, the heats of formation have been correlated with their unit cell volume (Vobs) and volume contraction ∆V %.59,60 7 Environment ACS Paragon Plus


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Since in the formation of a compound the volume contraction is proportional to its heat of formation,61,62 the trend of the observed ∆V % along the R3Pd5 series indicates an increasing thermodynamic stability of the binaries from Gd to Lu and Sc. To check for the type of formation of these phases, DTA analyses were carried out on Gd, Tb, Tm, and on Sc and Y alloys, on their 2:3 and 3:5 nominal compositions. Generally, DTA cooling curves showed three main thermal effects: a first peak due to the liquidus (L) (crystallization of the primary, congruently forming R3Pd4 phase), a second peak indicating the formation of the R3Pd5 compound (peritectic reaction: L + R3Pd4 R3Pd5), and a third peak likely corresponding to a eutectic reaction. An additional peak has been observed (both on heating and cooling) for Tb, Ho, Tm and Y samples, appearing at a lower temperature than that assumed to be the eutectic temperature; this feature was previously observed also in “R2Pd3” compounds, and it was associated with a structural transformation of the “2:3” phases.1-3 The Gd3Pd5 phase was observed only in ascast alloys. Several attempts to obtain this compound at room temperature gave negative results: samples annealed at 1130°C, 1145°C and 1155°C and ice/water quenched were biphasic, containing Gd3Pd4 and “GdPd2” (whose exact composition is Gd10Pd2141). DTA data confirm the formation of Gd3Pd5 by a peritectic reaction at 1170°C (Gd3Pd4 + L Gd3Pd5), close to 1160°C reported in Ref. 1 as the formation temperature of the “Gd2Pd3” phase,1 while the last thermal effect detected at 1135°C suggests its decomposition by a eutectoid reaction (Gd3Pd5 Gd3Pd4 + Gd10Pd21); this latter value is in a good agreement with the decomposition of this phase reported at 1130°C.1 It was not possible to quench Gd3Pd5 to room temperature and retain it (as a metastable phase) likely due to the very narrow temperature range of existence of this compound. The temperatures measured for the peritectic formation of the R3Pd5, with R = Sc, Y, Gd, Tb and Tm, along with the literature values given for the “R2Pd3”phases (for which data were available), are collected in Table 7. Figure 8b shows the trend of the formation temperature (Tf) as a function of the R3+ ionic radius. The formation temperature of these compounds increases almost linearly from Gd to Lu, with Sc and Y showing minor deviations from the trend. The Tf value for the Yb3Pd5 compound, being well in trend with the values of the other member of this series, further suggests a trivalent state for Yb, corroborating what argued from the lattice parameters data (paragraph 3.1). The literature value for Ce3Pd5 appears in some way to follow the same trend, even though it crystallizes in a different crystal structure (hexagonal Th3Pd5-type). The melting point of a compound can be related to its stability;59,60 therefore, such a trend would reflect the increasing thermodynamic stability of the R3Pd5 compounds with decreasing R3+ ionic size. Revised versions of the binary Gd-Pd and Ho-Pd phase diagrams are shown in Figures 9a and 9b, respectively. In the two systems the temperature of the peritectic formation of the R3Pd5 8 Environment ACS Paragon Plus

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compound, that of the eutectic reaction, and either the catatectic decomposition for Gd3Pd5 or phase transition for Ho3Pd5, have been updated using the thermal data presented here (1170°C, 1160°C and 1135°C in the Gd diagram; 1285°C, 1270°C and 1140°C in the Ho diagram). Moreover, the composition of the “RPd2” compound has also been corrected to the true value of R10Pd21.41 Attempts to obtain the high temperature form of R3Pd5, by quick cooling of arc-melted alloys or by rapid quenching after annealing, were performed in samples with nominal composition 2:3 and 3:5 (e.g. a sample Ho3Pd5 rapidly quenched after annealing at 1250°C for 6 days); however, despite the well detectable thermal effect observed at lower temperature for the R3Pd5 compounds, only the Pu3Pd5 structure type could be observed. The melting point trend in a lanthanide compound series has also been shown to be related to the relative volume contraction.59 An interesting tendency is observed for the R3Pd5 compounds when the volume contraction is plotted as a function of the formation temperature (Figure 10). The values of ∆V increase with the Tf from Tb to Sc compound, apparently following a cubic curve, in agreement with their predicted thermodynamic stability.

3.3. Physical properties of the R3Pd5 compounds The magnetic susceptibility, χ(T), of Tb3Pd5, Dy3Pd5, Ho3Pd5 and Er3Pd5 was measured between 2 and 300 K and in applied field of 3 kOe; the data are plotted in Figures 11a to 11d. The low temperature susceptibility (insets of Figures 11a-11d) shows two peaks in all the four compounds, characteristic of antiferromagnetic transitions. Moreover, no hysteresis is observed between the zero-field-cooled (ZFC) and field-cooled (FC) data (not shown here), which is consistent with longrange antiferromagnetic (AFM) ordering below TN. The Néel temperatures, TN1 and TN2, taken to be the same as the peak temperatures, are 13.5 and 6.5 K for Tb3Pd5, 11.0 and 5.0 K for Dy3Pd5, 7.2 and 4.2 K for Ho3Pd5, and 5.1 and 3.6 K for Er3Pd5; both TN1 and TN2 decrease on going from Tb to Er compound. The inverse magnetic susceptibility, 1/χ(T), is shown in Figures 12a-12d; for all of the four compounds it varies linearly with temperature above 100 K. The least squares fitted values of the effective paramagnetic moments, µeff, inferred from fitting the Curie-Weiss law [χ = C/(T−θp)] to the inverse susceptibility data between 150 and 300 K, are 9.64, 10.54, 10.60 and 9.74 µB/R for Tb3Pd5, Dy3Pd5, Ho3Pd5 and Er3Pd5, respectively, which are quite close to the Hund’s rule derived theoretical values for the corresponding rare earth R3+ ion.63 The negative values of the paramagnetic Curie temperature, θP, of −11, −26, −4 and −0.4 K for Tb3Pd5, Dy3Pd5, Ho3Pd5, and Er3Pd5, respectively, indicate antiferromagnetic ground states in these compounds. The Curie-Weiss parameters, along with the corresponding TN, are reported in Table 8. Figure 13 shows the trend of TN1 and TN2 as a function of either the R atomic number Z(R) (Figure 13a) or the de Gennes factor [(g–1)2 J(J+1), where g is the Landé g-factor and J is the total angular magnetic moment] (Figure



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13b). The de Gennes scaling is followed along the series, with a progressive and almost linear decreasing of the TN values on going from the lighter to the heavier R. The least-squares fit to the data allowed us to calculate an extrapolated value of TN1 ≈ 20 K and TN2 ≈ 8 K for the Gd3Pd5 compound, for which it was not possible to obtain a single phase sample to be measured. It may be noted that there are two in-equivalent crystallographic sites available in the unit cell for the rare earth ions R3+. In principle, the two rare earth sublattices could order magnetically at two distinct temperatures. Our data cannot distinguish that possibility from the one where both sublattices undergo two magnetic transitions simultaneously. The magnetic susceptibility of Y3Pd5, with very weak temperature dependence between 300 and 2 K, shows it to be a Pauli paramagnet; it increases from 1.5 × 10−4 to 3 × 10−4 emu/g, as the temperature is lowered from 300 down to 2 K. The isothermal magnetization, M(H), was measured up to 140 kOe at selected temperatures below the AFM transitions in these compounds; the data are plotted in Figures 14a, 14b, 14c, and 14d (the insets show the data on an expanded scale at low fields). The field dependence of the magnetization agrees with the AFM nature of these compounds. In Ho3Pd5 the magnetization increases with field without any apparent field-induced transitions below TN and shows no sign of saturation even up to 140 kOe. A small step in the magnetization is seen at four selected temperatures of 2, 5, 10 and 15 K, the last two above TN1 in the paramagnetic state; therefore, we believe it is due to some experimental artifact and not representing real transitions. Saturation at the highest field is not achieved in the other three compounds as well, but one sees evidence of fieldinduced magnetic transitions. In Tb3Pd5 the magnetization data at 2 and 5 K show clear evidence of field-induced transitions with hysteresis, indicating their first-order nature. Similarly, in Dy3Pd5 the magnetization at 2 K shows three field-induced transitions. The magnetization of Er3Pd5 at 2 K shows signatures of field-induced transitions near 3 and 10 kOe, which are poorly discernible at 3.5 K. The magnetization at 140 kOe does not attain the maximum free ion values, presumably due to both the crystal electric field effects and the fact that saturation has not yet been achieved. The zero field heat capacity data, CP, have been measured between 2 and 20 K for Y3Pd5, Tb3Pd5, Dy3Pd5, Ho3Pd5 and Er3Pd5 and the data are shown in Figures 15a and 15b. The plots reveal two prominent peaks for the Tb, Dy, Ho and Er compounds which correspond to the two magnetic transitions seen in the susceptibility data. The heat capacity of the Tb compound shows an extra third peak close to 5 K. This peak is relatively smaller and unlikely to be associated with a bulk transition of the main phase; we believe it is likely due to the parasitic impurity Tb3Pd4 phase. The heat capacity of Pauli-paramagnetic Y3Pd5 (plotted in Figure 15a) increases monotonically with temperature and represents contributions from conduction electron and phonon density of states. Below 5 K, the CP/T versus T2 (where CP is the heat capacity and T is the temperature) in Y3Pd5 is


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linear. The fit yields the electronic heat capacity γ = 4.8 mJ/mol K2 and the phonon heat capacity β = 1.6948 mJ/mol K4, which corresponds to a Debye temperature of 209.4 K. The 4f-contribution to the heat capacity, C4f, of the magnetic R3Pd5 (R = Tb, Dy and Er) compounds was derived by assuming that the phonon density of states of R3Pd5 is identical to that of the paramagnetic Y3Pd5. The phonon heat capacity of Y3Pd5 is suitably normalized to take into account the differing atomic masses of Y and the R ions64 and subtracted from the total heat capacity of R3Pd5 to obtain C4f. The heat capacity for the Tb, Dy and Er analogs was smoothly extrapolated to 0 K to obtain C4f below the lowest temperature of 1.8 K. The quantity C4f/T was integrated against T to obtain the entropy S4f which is plotted in Figure 16. Since the heat capacity of Ho3Pd5 is substantial even at 1.8 K (about 10 J/mol K), we have not calculated the entropy for this compound. For Dy3Pd5, S4f attains the value Rln2 (= 5.76 J/R mol K) in the vicinity of TN1 indicating a doublet ground state. The slow increase of S4f above TN1 indicates that the first excited crystal electric field level is not too close to the ground state. In Tb3Pd5 the entropy associated with a doublet state, Rln2, is attained at near 11 K, a few degrees below TN1. This suggests a contribution from the excited crystal electric field level(s) and, therefore, the first excited crystal electric field level may be relatively close to the ground state in this compound. In Er3Pd5, TN1 ≈ 5K but S4f attains a value of Rln2 only near 10 K (≈ 2 TN1). Prima-facie one may ascribe it to the presence of appreciable short range order above TN1. The temperature dependence of the electrical resistivity, ρ(T), has been measured between 2 and 300 K (in zero magnetic field) for Y3Pd5, Tb3Pd5, Ho3Pd5 and Er3Pd5; Figure 17 shows the data from 2 to 300 K. The resistivity of the four compounds decreases with decreasing temperature, exhibiting a typical metallic behavior. A sharp change in the slope is seen at TN1 in Tb3Pd5 and the resistivity decreases faster due to the gradual freezing of the spin-disorder resistivity below TN1; a milder anomaly at TN2 is also discernible (Figure 18a). Anomalies at the two magnetic transitions are also noticed in Ho3Pd5 and Er3Pd5 (Figure 18a). For Er3Pd5 measurements have also been performed under applied magnetic field. A gradual shift of the anomalies at TN1 and TN2 to lower temperatures with increasing field is observed. At low fields, ≈ 10 kOe, the anomalies are quite discernible but at higher fields they become weaker and less discernible and the prominent drop of the resistivity below TN1 observed in zero and low fields nearly disappears at 80 kOe (Figure 18b). These changes in the resistivity are qualitatively in conformity with the expected effect of the applied field on the antiferromagnetic configuration of the rare earth ions. The applied field tends to break the antiferromagnetic coupling of the moments and increases the spin disorder. As a result the resistivity below TN increases as observed experimentally; i.e. there is a positive magnetoresistance (MR). The positive MR below TN increases with increasing field up to 80 kOe, the highest field applied. In the paramagnetic state the field is expected to suppress the spin fluctuations and lead to a 11 Environment ACS Paragon Plus


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negative MR. But a positive MR is seen. Apparently, the positive contribution to MR due to the cyclotron motion of the conduction electrons predominates in the paramagnetic state; it will be present below TN as well. Overall, the electrical resistivity data corroborate magnetization and heat capacity data in identifying two magnetic transitions. As expected, the resistivity of Pauli paramagnetic Y3Pd5 does not show any anomalies.

3.4. Electronic structures The electronic densities of states (DOS) were calculated for Y3Pd5 and Gd3Pd5, to forecast the magnetic behavior of the latter compound for which it was not possible to perform magnetic measurements. The curves for Y3Pd5 and Gd3Pd5 are qualitatively similar in the range above –6 eV (Figure 19), with broad contributions of s and p states from both R and Pd and large, predominately Pd-4d states located ≈ 2-4 eV below EF. The contributions from Y are smaller but still significant, especially around 4 eV below EF, and become comparable at –1.7 eV and above. It should also be noted that contributions from Y s and p states are comparable to those of Pd s and p over the entire range, while Pd d contributions remain dominant until –1.7 eV. Local minima in the DOS curves are observed at the Femi level, while narrow but deep pseudo-gaps can be found at –0.8 eV. The positions of the pseudo-gaps in both compounds correspond to a difference of nearly one valence electron per formula unit, pointing towards the possible existence of new phases of the Pu3Pd5-type formed with palladium and divalent cations. Indeed, a large variety of representatives of this prototype, formed by alkaline earth and rare earth metals in combination with triels and tetrels, are found in the.3,4,65 An analysis of the representative compounds of the Pu3Pd5-type reveals a wide range for the valence electron concentrations, i.e. 9-29 valence electrons/f.u., thus suggesting only a minor influence of electronic factors on the structural stability. Spin polarized calculations were performed for two different spin ordering models of Gd3Pd5: a ferromagnetic and an antiferromagnetic scenario (assuming Gd moments at z = 0 and 0.25 to align antiparallel to those at z = 0.5 and 0.75). Full structural and positional optimizations have been performed prior to the total energy calculations. A comparison of the total energies shows 52 meV preference for the antiferromagnetic ordering that is in full agreement with the results of magnetic measurements for all the other R3Pd5 with heavy lanthanides (see paragraph 3.3.). The difference in positions of the 4f bands for the two symmetrically inequivalent Gd sites of 0.35 eV (7.90 and 8.25 eV below EF) is consistent with the presence of two antiferromagnetic transitions observed for the series R3Pd5 with different rare earths, and suggests different ordering temperatures for R1 and R2 opposed to canted antiferromagnetic interactions or simultaneous ordering of the two sites. The calculated magnetic moments per gadolinium atom in Gd3Pd5 range from 7.27 µB for Gd1 and 7.36 µB for Gd2. The magnetic moments due to f electrons are almost identical and approach 7 µB/Gd, 12 Environment ACS Paragon Plus

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while the remaining contributions are from spin polarized d electrons because of indirect 4f-4f exchange interactions.

4. Conclusions The earlier reported “R2Pd3” phases in fact correspond to the composition R3Pd5 and they adopt the Pu3Pd5-type crystal structure [oS32, Cmcm (No. 63)]. This phase forms for all of the heavy lanthanides from Gd to Lu, plus Y and Sc. Gd3Pd5 is a high temperature phase existing in a very narrow temperature range; this was the main reason it was not possible to quench this compound at room temperature as a metastable phase. The R3Pd5 compounds represent the first example of a binary phase formed by R and Pd crystallizing in the Pu3Pd5 structure type. A value of 29.74 Å3 has been derived for the atomic volume of Yb in the hypothetical trivalent metallic state (in standard conditions); such a value, missing in literature, could be hereafter used for crystal-chemistry and valence behavior considerations on Yb-based intermetallic compounds. All R3Pd5 compounds form by peritectic reactions. The formation temperatures have been measured for some members of the series. In the light of our results, all the corresponding R-Pd phase diagrams have to be updated and some of them should be reinvestigated too. Both the trends of the volume contraction and formation temperature along the series indicate an increase in the thermodynamic stability of the R3Pd5 compounds in the row from the Gd to Lu and Sc compounds. The magnetization, heat capacity and zero field electrical resistivity have been measured for some representative members of the series (Tb3Pd5, Dy3Pd5, Ho3Pd5, Er3Pd5 and Y3Pd5). Two antiferromagnetic transitions, TN1 and TN2, are observed for Tb, Dy, Ho and Er compounds at low temperatures, likely associated to the two rare earth sublattices present in the Pu3Pd5-type structure (pertaining to the 4c and 8e sites). For the Gd3Pd5 compound the linear fit of TN data, as a function of the de Gennes factor, allowed us to determine extrapolated values of ≈ 20 K and ≈ 8 K for TN1 and TN2, respectively. The electronic structure calculations predict antiferromagnetic ordering in Gd3Pd5, which accords well with the antiferromagnetic transitions observed in iso-structural R3Pd5 (R = Tb, Dy, Ho and Er). The calculated magnetic moments of 7.27µB for Gd1 and 7.36 µB for Gd2 are close to the Hund’s rule derived value for free ion Gd3+. The difference in positions of the 4f bands for the symmetrically in-equivalent Gd positions is consistent with two antiferromagnetic transitions.

ACKNOWLEDGMENTS A. Provino would like to thank the University of Genova for supporting the research leave in 2015. The research was partly supported by the Office of the Basic Energy Sciences, Materials Sciences



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and Engineering Division of the USDOE Ames Laboratory is operated for DOE by Iowa State University under contract DE-AC02-07CH11358.

REFERENCES (1)

Loebich Jr., O.; Raub, E. J. Less-Common Met. 1973, 30, 47-62.

(2)

Massalski, T. B. in Binary Alloy Phase Diagrams, 2nd ed.; ASM International: Metals Park, OH, USA, 1990.

(3)

ASM International, Alloy Phase Diagrams, Online ed.; 2006; Vol. 3.

(4)

Villars, P.; Calvert, L.D. in Pearson’s Handbook of Crystallographic Data for Intermetallic Compounds, 2nd ed.; ASM International: Metals Park, OH, USA, 1991.

(5)

Villars, P.; Cenzual, K. in Pearson’s Crystal Data-Crystal Structure Database for Inorganic Compounds; ASM International: Materials Park, OH, USA, Release 2010/11.

(6)

Iandelli, A.; Palenzona, A. J. Less-Common Met. 1974, 38, 1-7.

(7)

Iandelli, A.; Palenzona, A. Rev. Chim. Minér. 1973, 10, 303-308.

(8)

Lukas, H. L.; Fries, S.G.; Sundman, B. in Computational Thermodynamics; Cambridge University Press: New York, 2007.

(9)

Du, Z.; He, Y. J. Alloy Compd. 2001, 327, 127-131.

(10) Du, Z.; Yang, H. J. Alloy Compd. 2000, 312, 181-188. (11) Du, Z.; Yang, H.; Xu, Y. J. Alloy Compd. 2000, 302, 199-203. (12) Du, Z.; Yang, H. J. Alloy Compd. 2000, 299, 199-204. (13) Du, Z.; Yang, H.; Li, C. J. Alloy Compd. 2000, 297, 185-191. (14) Borzone, G.; Cacciamani, G.; Ferro, R. Calphad 1990, 14, 139-149. (15) Kolchugina, N. B.; Burkhanov, G. S.; Drapala, J. Russ. Metall. 2011, 7, 634-639. (16) Ilyushin, A. S.; Khatanova, N. A.; Rykova, E. A.; Silonova, E. V. Vestn. Mosk. Univ. Ser. 3. Fiz. Astronom. 2001, 2, 47-51. (17) Cromer, D. T. Acta Crystallogr. B 1976, 32, 1930-1932. (18) Kim, S. J.; Fäsler, T. F. Z. Anorg. Allg. Chem. 2009, 635, 1925-1932. (19) Klem, M. T.; Vaughey, J. T.; Harp, J. G.; Corbett, J. D. Inorg. Chem. 2001, 40, 7020-7026. (20) Bruzzone, G.; Franceschi, E. A. J. Less-Common Met. 1977, 52, 211-216. (21) Budnyk, S. L.; Grin, Y.; Weitzer, F.; Kubata, C.; Prots, Y. M.; Akselrud, L. G.; Schnelle, W.; Hiebl, K.; Nesper, R.; Wagner, F. R. J. Solid State Chem. 2006, 179, 2329-2338. (22) Palenzona, A.; Manfrinetti, P.; Fornasini, M. L. J. Alloy Compd. 1998, 280, 211-214. (23) Manfrinetti, P.; Mazzone, D.; Palenzona, A. J. Alloy Compd. 1999, 284, L1-L3. (24) Harada, M.; Fukuoka, H.; Matsumura, D.; Inumaru, K. J. Phys. Chem. C 2012, 116, 2153215. 14 Environment ACS Paragon Plus

Page 14 of 66

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(25) McMasters, O. D.; Gschneidner Jr., K. A. J. Less-Common Met. 1974, 38, 137-148. (26) Borzone, G.; Borsese, A.; Ferro, R. Z. Anorg. Allg. Chem. 1983, 501, 199-208. (27) Delfino, S.; Saccone, A.; Mazzone, D.; Ferro, R. J. Less-Common Met. 1981, 81, 45-53. (28) Delfino, S.; Saccone, A.; Ferro, R. Z. Metallkd. 1980, 71, 165-171. (29) Borzone, G.; Borsese, A.; Ferro R. J. Less-Common Met. 1982, 85, 195-203. (30) Delfino, S.; Saccone, A.; Ferro, R. J. Less-Common Met. 1979, 65, 181-190. (31) Eremenko, V. N.; Bulanova, M. V.; Listovnichii, V. E.; Petyukh, V. M. Ukr. Khim. Zh. 1988, 54, 787-795 [Sov. Prog. Chem. 1988, 54, 1-7 (English Transl.)]. (32) Delfino, S.; Saccone, A.; Borzone, G.; Ferro, R. J. Less-Common Met. 1978, 59, 69-78. (33) Sabirzyanov, N. A.; Gryniv, I. A.; Yatsenko, S. P. Izv. Akad. Nauk SSSR Met. 1989, 3, 190193 [Russ. Metall. 1989, 3, 182-184 (English Transl.)]. (34) Pötzschke, M.; Schubert, K. Z. Metallkd. 1962, 53, 474-488. (35) Cenzual, K.; Jorda, J. L.; Parthé, E. Acta Crystallogr. C 1988, 44, 14-18. (36) Palenzona, A.; Manfrinetti, P.; Cirafici, S. J. Less-Common Met. 1984, 97, 231-236. (37) Palenzona, A.; Cirafici, S.; Canepa, F. J. Less-Common Met. 1985, 114, 311-316. (38) Buschow, K. H. J. J. Less-Common Met. 1973, 31, 165-168. (39) Kappler, J. P.; Besnus, M. J.; Lehmann, P.; Meyer, A.; Sereni, J. G. J. Less-Common Met. 1985, 111, 261-264. (40) Provino, A.; Manfrinetti, P.; Gschneidner Jr., K. A.; Dhar, S. K. XLI National Congress of Physical Chemistry, Alessandria, Italy, June 23-27, 2013. (41) Provino, A.; Sangeetha, N. S.; Dhar, S. K.; Manfrinetti, P.; Mazzone, D.; Gschneidner Jr., K. A. 19th Conference on Solid Compounds of Transition Elements (SCTE-2014), Genova, Italy, 21-26 June, 2014. (42) Provino, A.; Dhar, S. K.; Sangeetha, N. S.; Manfrinetti, P.; Petit, L.; Gschneidner Jr., K. A. 20th International Conference on Magnetism (ICM-2015), Barcelona, Spain, July 5-10, 2015. (43) Yvon, K.; Jeitschko, W.; Parthé, E. J. Appl. Crystallogr. 1977, 10, 73-74. (44) SMART software package, Siemens Analytical X-ray Instruments Inc., Madison, WI, USA, 1996. (45) Blessing, R. Acta Crystallogr. A 1995, 51, 33-38. (46) SADABS program, Bruker AXS Inc., Madison, WI, USA, 2001. (47) SHELXTL, Bruker AXS Inc., Madison, WI, USA, 2000. (48) Rodriguez-Carvajal, J. Physica B 1993, 192, 55-69, http://www.ill.eu/sites/fullprof/php/downloads.html. (49) Blöchl, P. E. Phys. Rev. B 1994, 50, 17953-17979.



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(50) Kresse, G.; Marsman, M.; Furthmüller, J. Vienna ab-initio simulation package, VASP, the user Guide, 2010. (51) Kresse, G.; Furthmüller, J. Comp. Mater. Sci. 1996, 6, 15-50. (52) Kresse, G.; Furthmüller, J. Phys. Rev. B 1996, 54, 11169-11186. (53) Kresse, G.; Hafner, J. Phys. Rev. B 1993, 47, 558-561. (54) Kresse, G.; Joubert, D. Phys. Rev. B 1999, 59, 1758-1775. (55) Villars, P.; Daams, J. L. C. J. Alloy Compd. 1993, 197, 177-196. (56) Shannon, R. D. Acta Crystallogr. A 1976, 32, 751-767. (57) Gschneidner Jr., K. A. J. Less-Common Met. 1969, 17, 13-24. (58) Teatum, E.; Gschneidner Jr., K. A.; Waber, J. Report LA-4003, NTIS, Springfield, VA, 1968. (59) Gschneidner Jr., K. A. J. Less-Common Met. 1969, 17, 1-12. (60) Manfrinetti, P.; Provino, A.; Gschneidner Jr., K. A. J. Alloy Compd. 2009, 482, 81-85. (61) Kubaschewski, O.; Alcock, C. B.; Spencer, P. J. in Materials Thermochemistry, 6th ed.; Pergamon Press: Oxford, 1993. (62) Gschneidner Jr., K. A. Met. Mater. Processes 1990, 1, 241-251. (63) Handbook on the Physics and Chemistry of Rare Earths; Gschneidner Jr., K. A., Eyring, L., Eds.; North-Holland Physics Publishing: Amsterdam, 1978; Vol. 1. (64) Bouvier, M.; Lethuillier, P.; Schmitt, D. Phys. Rev. B 1991, 43, 13137-13144. (65) Inorganic Crystal Structure Database (ICSD); Fiz Karlsruhe, Germany, 2016.


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FIGURES CAPTION Figure 1. SEM photo [backscattered electron (BSE) mode] of a sample with nominal composition ‘Ho2Pd3’ (annealed at 1160ºC for 3 days and quenched). Biphasic sample: primary dendritic crystals of Ho3Pd4 (light-gray phase) in a matrix of Ho3Pd5 (dark-gray phase). Figure 2. Trend of the lattice parameters vs. the rare earth ionic radius (R3+) for the R3Pd5 compounds [orthorhombic Pu3Pd5-type, oS32, Cmcm (No. 63)]. The empty symbols are the expected values for Sc containing compounds (extrapolated from linear regression of the data from Gd to Lu). Figure 3. Trend of the observed unit cell volume (Vobs) vs. the R3+ ionic radius for the R3Pd5 compounds. Solid line is the linear fit to the Gd-to-Lu data only. Figure 4. Observed X-ray powder pattern (red circle) and Rietveld refinement profile (black line) for Tb3Pd5 (a), Ho3Pd5 (b) and Tm3Pd5 (c) samples [the symbol (*) in (b) and (c) indicates an extra reflection pertaining to R2O3]. The lower profile (blue line) gives the difference between observed and calculated data; the Bragg angle positions are indicated by vertical bars (green). Figure 5. Sketch of the crystal structure of the Tb3Pd5 compound [orthorhombic Pu3Pd5-type, oS32, Cmcm (No. 63)]. The polyhedron around Tb1 (highlighted in blue; CN = 13: Tb4@Pd9) and Tb2 (highlighted in green; CN = 15: Tb5@Pd10) atoms also shown. Figure 6. Projections of the crystal structure of Tb3Pd5 along the b-axis (a) and c-axis (b), respectively. Figure 7. (a) View of the crystal structure for Tb3Pd5 along the a-axis, where only the shorter Tb1−Tb2 interatomic distances (along the c-axis) are shown. (b) Perspective view of the structure along the c-axis, where the shortest Tb2−Tb2 interatomic distances (on the a-b plane) are highlighted. In both figures Pd atoms have been hid for simplicity. Figure 8. (a) Trend of the volume contraction (∆V %) as a function of the R3+ ionic radius (data point for Yb is an interpolated value); (b) values of the peritectic temperature, Tf, measured for the R3Pd5 (full circles) along with the literature data given for the formation of the “R2Pd3” phases (empty circles), plotted vs. the R3+ ionic radius. The dashed line is an eye-trace. Figure 9. Updated version of the binary Gd-Pd (a) and Ho-Pd (b) phase diagrams. Figure 10. Trend of the volume contraction (∆V %) vs. the peritectic temperature, Tf, for the R3Pd5 compounds (either determined in this work or literature data for the “R2Pd3”). The dashed line is the fit to a cubic function. Figure 11. DC magnetic susceptibility, χ(T), vs. temperature measured between 2 and 300 K and at 3 kOe for Tb3Pd5 (a), Dy3Pd5 (b), Ho3Pd5 (c) and Er3Pd5 (d). The insets show the susceptibility on enlarged scale (data recorded at 180 Oe for Er3Pd5).



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Figure 12. Inverse magnetic susceptibility, 1/χ(T), measured between 2 and 300 K at 3 kOe for Tb3Pd5 (a), Dy3Pd5 (b), Ho3Pd5 (c) and Er3Pd5 (d); the straight line is the fit to the Curie-Weiss law. Figure 13. The Néel temperatures, TN1 and TN2, of the R3Pd5 compounds with R = Tb, Dy, Ho and Er plotted vs. the R atomic number, Z(R), (the dashed lines are a trace to the eye) (a), and vs. the de Gennes factor (the solid lines are least-squares fits; the dashed lines are a linear extrapolation to obtain estimated values for Gd3Pd5) (b). Figure 14. Isothermal magnetization, M(H), up to 140 kOe, measured at 2, 5, 10 and 15 K for Tb3Pd5 (a), at 2 K and 5 K for Dy3Pd5 (b), at 2, 5, 10 and 15 K for Ho3Pd5 (c) and at 2, 3.5 and 6 K for Er3Pd5 (d). The insets show the data between 0 and 20 kOe (0-40 kOe for Dy3Pd5). Figure 15. Zero field heat capacity, CP, vs. temperature for Y3Pd5, Tb3Pd5 and Dy3Pd5 in the range 2-20 K (a) and Ho3Pd5 and Er3Pd5 in the range 2-14 K (b). Figure 16. Entropy S4f as a function of temperature in Tb3Pd5, Dy3Pd5 and Er3Pd5 compounds. Figure 17. Zero field electrical resistivity, ρ(T), of Y3Pd5, Tb3Pd5, Ho3Pd5 and Er3Pd5 between 2 and 300 K. Figure 18. Electrical resistivity, ρ(T), of Y3Pd5, Tb3Pd5 and Ho3Pd5 between 2 and 40 K (a) and infield electrical resistivity of Er3Pd5 between 2 and 10 K measured at several applied magnetic fields (b). Figure 19. (a) Total and projected DOS curves for Y3Pd5 (Y in red, Pd in violet, total in black); (b) spin polarized total and projected DOS curves for Gd3Pd5 for an AFM spin ordering model (Gd in red and orange, Pd in violet and green, total in black). The Fermi levels are represented by dashed lines.


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Table 1. The R-Pd binary phases reported in literature.

R-Pd

R4Pd

R3Pd

R5Pd2

R7Pd3

R2Pd

R3Pd2

RPd

R3Pd4

R2Pd3

RPd1.63

R3Pd5

RPd2

R10Pd21

RPd2.13

R2Pd5

RPd3

RPd5

RPd7

at.% R

80

75

71.43

70

66.67

60

50

42.86

40

38.02

37.5

33.3

32.26

31.95

28.57

25

16.67

12.5

Sc

-

-

-

-

-

-

-

-

-

-

-

-

-

Y

-

-

-

-

-

-

-

-

-

La

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Ce

-

-

-

-

-

-

-

-

-

-

Pr

-

-

-

-

-

-

-

-

-

-

-

Nd

-

-

-

-

-

-

-

-

-

-

-

-

Sm

-

-

-

-

-

-

-

-

-

-

Eu

-

-

-

-

-

-

-

-

-

-

-

-

-

Gd

-

-

-

-

-

-

-

-

-

-

-

Tb

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Dy

-

-

-

-

-

-

-

-

-

-

Ho

-

-

-

-

-

-

-

-

-

-

-

-

Er

-

-

-

-

-

-

-

-

-

-

-

Tm

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Yb

-

-

-

-

-

-

-

-

-

-

-

Lu

-

-

-

-

-

-

-

-

-

-

-

-

19

ACS Paragon Plus Environment


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Page 20 of 66

Table 2. Lattice parameters (a, b, c), observed unit cell volume (Vobs) and volume contraction (∆V%) for the R3Pd5 compounds [orthorhombic Pu3Pd5-type, oS32,Cmcm (No. 63)].

Lattice parameters R3Pd5

Vobs [Å3]

∆V %

R3+ [Å]

a [Å]

b [Å]

c [Å]

Gd3Pd5

9.188(3)

7.137(2)

9.659(3)

633.40

8.34

0.938

Tb3Pd5

9.149(2)

7.106(1)

9.607(2)

624.65

8.05

0.923

Dy3Pd5

9.122(2)

7.086(1)

9.554(2)

617.54

8.11

0.908

Ho3Pd5

9.101(2)

7.070(1)

9.506(1)

611.68

8.33

0.894

Er3Pd5

9.076(1)

7.054(2)

9.462(2)

605.80

8.42

0.881

Tm3Pd5

9.046(1)

7.030(1)

9.411(1)

598.43

8.64

0.869

Yb3Pd5

9.027(2)

7.016(1)

9.367(2)

593.30

8.81*

0.858

Lu3Pd5

9.005(1)

7.006(1)

9.336(2)

589.01

9.08

0.848

Sc1.5Lu1.5Pd5

8.892(1)

6.954(1)

9.108(2)

563.22

9.28

0.829

Sc3Pd5

8.737(2)

6.848(1)

8.957(2)

535.87

9.76

0.810

Y3Pd5

9.132(2)

7.100(1)

9.550(1)

619.27

10.50

0.910

* Interpolated value for Yb3Pd5, see paragraph 3.2.

20 ACS Paragon Plus Environment

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Table 3. Rietveld refinement data for Tb3Pd5, Ho3Pd5 and Tm3Pd5 compounds [orthorhombic Pu3Pd5-type, oS32, Cmcm (No. 63)].

Atomic coordinates Atom

Wyckoff site

Occupation x

y

z

Tb(1)

4c

0

0.6260(1)

1/4

1

Tb(2)

8e

0.2011(1)

0

0

1

Pd(1)

4c

0

0.0215(2)

1/4

1

Pd(2)

8f

0

0.3192(1)

0.0382(1)

1

Pd(3)

8g

0.2157(1)

0.2898(1)

1/4

1

Ho(1)

4c

0

0.6164(1)

1/4

1

Ho(2)

8e

0.2009(1)

0

0

1

Pd(1)

4c

0

0.0147(1)

1/4

1

Pd(2)

8f

0

0.3073(1)

0.0438(1)

1

Pd(3)

8g

0.2237(1)

0.2825(1)

1/4

1

Tm(1)

4c

0

0.6168(2)

1/4

1

Tm(2)

8e

0.2001(1)

0

0

1

Pd(1)

4c

0

0.0161(2)

1/4

1

Pd(2)

8f

0

0.3186(2)

0.0417(1)

1

Pd(3)

8g

0.2235(1)

0.2792(2)

1/4

1

a = 9.1544(3) Å, b = 7.1108(2)Å, c = 9.6135(3) Å Tb3Pd5

RB = 1.3 %, RF = 3.5 %, Rwp = 9.5 %, χ2 = 1.3 %, Bover = 3.17(2) Å2 a = 9.09728(4) Å, b = 7.07172(3)Å, c = 9.50915(4) Å Rwp = 13.6 %, χ2 = 1.48, Bover.= 1.103(9) Å2

Ho3Pd5 Fraction % Ho3Pd5: 92.5(5) %, RB = 1.84 %, RF = 2.13 % Fraction % Ho3Pd4: 7.5(2) %, RB = 4.53 %, RF = 4.61 % a = 9.0487(1) Å, b = 7.0306(1) Å, c = 9.4121(2) Å Tm3Pd5

RB = 0.9 %, RF = 1.7 %, Rwp = 6.4 %, χ2 = 1.8 %, Bover = 2.90(1) Å2



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Table 4. Details of the crystal structure investigation and refinement for Tb3Pd5 (T = 293 K).

Compound

Tb3Pd5

Formula Weight [g/mol]

1008.76

Structural prototype

Pu3Pd5

Pearson symbol

oS32

Crystal system

Orthorhombic

Space group

Cmcm (No. 63)

a [Å]

9.135(2)

b [Å]

7.105(1)

c [Å]

9.5870(2)

Unit cell volume [Å3]

622.2(2)

Unit formula per cell, Z

4

Calculated density, ρ [g/cm3]

10.768

Absorption coefficient, µ [mm-1]

47.570

F(000)

1700

Crystal size [mm]

0.05 × 0.06 × 0.08

Theta range [deg]

3.63º ≤ ϑ ≤ 29.10º 0 ≤ h ≤ 12

Index ranges h, k, l

–9 ≤ k ≤ 9 –13 ≤ l ≤ 0

Reflections collected

790

Independent reflections

467

Absorption correction

Empirical

Refinement method

Full-matrix least-squares on F2

Refined parameters

27

Data/restraints/parameter 2

467/0/27

Goodness of fit on F

1.111

Final R indices [I > 2σ(I)]a

R1 = 0.0358, wR2 = 0.0645

R indices (all data)

R1 = 0.0495, wR2 = 0.0673

Rint

0.033

Largest diff. peak and hole [e–/Å3]

+2.560, –1.899


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Table 5. Standardized atomic coordinates, isotropic (Ueq) and anisotropic (U11, U22, U33, U12, U23, U13) displacement parameters of Tb3Pd5 compound [Pu3Pd5-type, oS32, Cmcm (No. 63)], as obtained from single crystal analysis; (U13 = 0).

x

Atomic coordinates y

z

4c

0

0.6176(2)

Tb(2)

8e

0.2026(1)

Pd(1)

4c

Pd(2)

Atom

Wyckoff site

Tb(1)

Occ.

Ueq [Å2]

1/4

1

0.0153(3)

0

0

1

0.0148(2)

0

0.0180(3)

1/4

1

0.0160(4)

8f

0

0.3120(2)

0.0471(2)

1

0.0167(3)

Pd(3)

8g

0.2226(2)

0.2805(2)

1/4

1

0.0176(3)

Atom

Wyckoff site

U11 [Å2]

U22 [Å2]

U33 [Å2]

U23 [Å2]

U12 [Å2]

Tb(1)

4c

0.0150(6)

0.0165(5)

0.0145(5)

0

0

Tb(2)

8e

0.0131(4)

0.0160(4)

0.0152(3)

−0.0004(3)

0

Pd(1)

4c

0.0156(8)

0.0164(8)

0.0159(8)

0

0

Pd(2)

8f

0.0155(6)

0.0168(6)

0.0178(6)

−0.0019(5)

0

Pd(3)

8g

0.0147(7)

0.0231(6)

0.0152(5)

0

0.0007(5)



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Page 24 of 66

Table 6. Interatomic distances, for dobs/ΣrM ≤ 1.106 (where dobs is the observed interatomic distance and ΣrM is the sum of the metallic radii58) in Tb3Pd5 compound, as obtained from single crystal analysis.

Central atom Ligands d [Å]

dobs/Σ ΣrM

Central atom Ligands d [Å]

dobs/Σ ΣrM

Tb1-

4Tb2

3.7177(8)

1.043

Pd1-

1Tb1

2.845(2)

0.901

CN = 13

2Pd3

3.142(2)

0.995

CN = 11

4Tb2

3.0311(7)

0.960

Tb4@Pd9

2Pd2

2.916(2)

0.923

Tb5@Pd6

2Pd2

2.855(2)

1.037

2Pd2

2.891(2)

0.915

2Pd3

2.759(2)

1.002

1Pd1

2.845(2)

0.901

2Pd3

3.045(2)

1.106

2Pd3

2.786(2)

0.882 Pd2-

1Tb1

2.891(2)

0.915

Tb2-

2Tb1

3.7177(8)

1.043

CN = 10

1Tb1

2.915(2)

0.923

CN = 15

1Tb2

3.7024(7)

1.039

Tb6@Pd4

2Tb2

2.923(1)

0.926

Tb5@Pd10

2Tb2

3.6563(8)

1.026

2Tb2

3.060(1)

0.969

2Pd2

2.923(1)

0.926

1Pd1

2.855(2)

1.037

2Pd3

2.9401(9)

0.931

1Pd2

2.819(3)

1.024

2Pd1

3.0311(7)

0.960

2Pd3

2.823(2)

1.026

2Pd2

3.060(1)

0.969

2Pd3

3.122(1)

0.989

Pd3-

1Tb1

3.142(2)

0.995

CN = 10

2Tb2

3.122(1)

0.989

Tb6@Pd4

1Tb1

2.786(2)

0.882

2Tb2

2.9401(9)

0.931

2Pd2

2.823(2)

1.026

1Pd1

3.045(2)

1.106

1Pd1

2.759(2)

1.003


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Table 7. Temperature values of the peritectic formation for the R3Pd5 compounds (DTA data), along with the literature values reported for the “R2Pd3” phases (when available).

R3Pd5

Tformation [ºC]

Reference

Ce3Pd5*

1037

literature data

“Pr2Pd3”

1033

literature data

Gd3Pd5

1170

this work

Tb3Pd5

1198

this work

Dy3Pd5

1245

literature data for “Dy2Pd3”

Ho3Pd5

1285

this work

Er3Pd5

1323

literature data for “Er2Pd3”

Tm3Pd5

1334

this work

Yb3Pd5

1360

literature data for “YbPd1.67”

Lu3Pd5

1375

literature data for “Lu2Pd3”

Sc3Pd5

1420

this work

Y3Pd5

1295

this work

* Th3Pd5-type



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Table 8. Transition temperatures and Curie-Weiss parameters for the R3Pd5 compounds (R = Tb, Dy, Ho and Er). The TN1 and TN2 data for Gd3Pd5 are extrapolated values (see Figure 13b).

R3Pd5

TN1 [K]

TN2 [K]

θP [K]

µeff [µB/R]

Gd3Pd5

≈ 20

≈8

-

-

Tb3Pd5

13.5

6.5

−11

9.64

Dy3Pd5

11.0

5.0

−26

10.54

Ho3Pd5

7.2

4.2

−4

10.60

Er3Pd5

5.1

3.6

−0.5

9.74


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Figure 1. SEM photo [backscattered electron (BSE) mode] of a sample with nominal composition ‘Ho2Pd3’ (annealed at 1160ºC for 3 days and quenched). Biphasic sample: primary dendritic crystals of Ho3Pd4 (light-gray phase) in a matrix of Ho3Pd5 (dark-gray phase).



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Figure 2. Trend of the lattice parameters vs. the rare earth ionic radius (R3+) for the R3Pd5 compounds [orthorhombic Pu3Pd5-type, oS32, Cmcm (No. 63)]. The empty symbols are the expected values for Sc containing compounds (extrapolated from linear regression of the data from Gd to Lu). . 28 ACS Paragon Plus Environment

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Figure 3. Trend of the observed unit cell volume (Vobs) vs. the R3+ ionic radius for the R3Pd5 compounds. Solid line is the linear fit to the Gd-to-Lu data only.



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Figure 4. Observed X-ray powder pattern (red circle) and Rietveld refinement profile (black line) for Tb3Pd5 (a), Ho3Pd5 (b) and Tm3Pd5 (c) samples [the symbol (*) in (b) and (c) indicates an extra reflection pertaining to R2O3]. The lower profile (blue line) gives the difference between observed and calculated data; the Bragg angle positions are indicated by vertical bars (green).


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Figure 5. Sketch of the crystal structure of the Tb3Pd5 compound [orthorhombic Pu3Pd5-type, oS32, Cmcm (No. 63)]. The polyhedron around Tb1 (highlighted in blue; CN = 13: Tb4@Pd9) and Tb2 (highlighted in green; CN = 15: Tb5@Pd10) atoms also shown.



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Figure 6. Projections of the crystal structure of Tb3Pd5 along the b-axis (a) and c-axis (b), respectively.


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Figure 7. (a) View of the crystal structure for Tb3Pd5 along the a-axis, where only the shorter Tb1−Tb2 interatomic distances (along the c-axis) are shown. (b) Perspective view of the structure along the c-axis, where the shortest Tb2−Tb2 interatomic distances (on the a-b plane) are highlighted. In both figures Pd atoms have been hid for simplicity.



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Figure 8. (a) Trend of the volume contraction (∆V %) as a function of the R3+ ionic radius (data point for Yb is an interpolated value); (b) values of the peritectic temperature, Tf, measured for the R3Pd5 (full circles) along with the literature data given for the formation of the “R2Pd3” phases (empty circles), plotted vs. the R3+ ionic radius. The dashed line is an eye-trace.


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Figure 9. Updated version of the binary Gd-Pd (a) and Ho-Pd (b) phase diagrams.



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Figure 10. Trend of the volume contraction (∆V %) vs. the peritectic temperature, Tf, for the R3Pd5 compounds (either determined in this work or literature data for the “R2Pd3”). The dashed line is the fit to a cubic function.


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Figure 11. DC magnetic susceptibility, χ(T), vs. temperature measured between 2 and 300 K and at 3 kOe for Tb3Pd5 (a), Dy3Pd5 (b), Ho3Pd5 (c) and Er3Pd5 (d). The insets show the susceptibility on enlarged scale (data recorded at 180 Oe for Er3Pd5). 37 ACS Paragon Plus Environment


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Figure 12. Inverse magnetic susceptibility, 1/χ(T), measured between 2 and 300 K and at 3 kOe for Tb3Pd5 (a), Dy3Pd5 (b), Ho3Pd5 (c) and Er3Pd5 (d); the straight line is the fit to the Curie-Weiss law. 38 ACS Paragon Plus Environment

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Figure 13. The Néel temperatures, TN1 and TN2, of the R3Pd5 compounds with R = Tb, Dy, Ho and Er plotted vs. the R atomic number, Z(R), (the dashed lines are a trace to the eye) (a), and vs. the de Gennes factor (the solid lines are least-squares fits; the dashed lines are a linear extrapolation to obtain estimated values for Gd3Pd5) (b).



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Figure 14. Isothermal magnetization, M(H), up to 140 kOe, measured at 2, 5, 10 and 15 K for Tb3Pd5 (a), at 2 K and 5 K for Dy3Pd5 (b), at 2, 5, 10 and 15 K for Ho3Pd5 (c) and at 2, 3.5 and 6 K for Er3Pd5 (d). The insets show the data between 0 and 20 kOe (0-40 kOe for Dy3Pd5). 40 ACS Paragon Plus Environment

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Figure 15. Zero field heat capacity, CP, vs. temperature for Y3Pd5, Tb3Pd5 and Dy3Pd5 in the range 2-20 K (a) and Ho3Pd5 and Er3Pd5 in the range 2-14 K (b).



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Figure 16. Entropy S4f as a function of temperature in Tb3Pd5, Dy3Pd5 and Er3Pd5 compounds.


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Figure 17. Zero field electrical resistivity, ρ(T), of Y3Pd5, Tb3Pd5, Ho3Pd5 and Er3Pd5 between 2 and 300 K.



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Figure 18. Electrical resistivity, ρ(T), of Y3Pd5, Tb3Pd5 and Ho3Pd5 between 2 and 40 K (a) and infield electrical resistivity of Er3Pd5 between 2 and 10 K measured at several applied magnetic fields (b).


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Figure 19. (a) Total and projected DOS curves for Y3Pd5 (Y in red, Pd in violet, total in black); (b) spin polarized total and projected DOS curves for Gd3Pd5 for an AFM spin ordering model (Gd in red and orange, Pd in violet and green, total in black). The Fermi levels are represented by dashed lines.



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Graphical abstract. Coordination polyhedra surrounding the two in-equivalent rare earth atoms, R1 and R2, in the unit cell of the orthorhombic Pu3Pd5-type R3Pd5 compounds, along with the trend of the Néel temperatures, TN1 and TN2, plotted vs. the de Gennes factor.


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Figure 1. SEM photo [backscattered electron (BSE) mode] of a sample with nominal composition ‘Ho2Pd3’ (annealed at 1160ºC for 3 days and quenched). Biphasic sample: primary dendritic crystals of Ho3Pd4 (lightgray phase) in a matrix of Ho3Pd5 (dark-gray phase). 26009x19507mm (1 x 1 DPI)



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Figure 2. Trend of the lattice parameters vs. the rare earth ionic radius (R3+) for the R3Pd5 compounds [orthorhombic Pu3Pd5-type, oS32, Cmcm (No. 63)]. The empty symbols are the expected values for Sc containing compounds (extrapolated from linear regression of the data from Gd to Lu). 153x213mm (300 x 300 DPI)


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Figure 3. Trend of the observed unit cell volume (Vobs) vs. the R3+ ionic radius for the R3Pd5 compounds. Solid line is the linear fit to the Gd-to-Lu data only. 82x62mm (300 x 300 DPI)



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Figure 4. Observed X-ray powder pattern (red circle) and Rietveld refinement profile (black line) for Tb3Pd5 (a), Ho3Pd5 (b) and Tm3Pd5 (c) samples [the symbol (*) in (b) and (c) indicates an extra reflection pertaining to R2O3]. The lower profile (blue line) gives the difference between observed and calculated data; the Bragg angle positions are indicated by vertical bars (green). 321x706mm (72 x 72 DPI)


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Figure 5. Sketch of the crystal structure of the Tb3Pd5 compound [orthorhombic Pu3Pd5-type, oS32, Cmcm (No. 63)]. The polyhedron around Tb1 (highlighted in blue; CN = 13: Tb4@Pd9) and Tb2 (highlighted in green; CN = 15: Tb5@Pd10) atoms also shown. 409x386mm (72 x 72 DPI)



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Figure 6. Projections of the crystal structure of Tb3Pd5 along the b-axis (a) and c-axis (b), respectively. 450x273mm (72 x 72 DPI)


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Figure 7. (a) View of the crystal structure for Tb3Pd5 along the a-axis, where only the shorter Tb1−Tb2 interatomic distances (along the c-axis) are shown. (b) Perspective view of the structure along the c-axis, where the shortest Tb2−Tb2 interatomic distances (on the a-b plane) are highlighted. In both figures Pd atoms have been hid for simplicity. 375x524mm (72 x 72 DPI)



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Figure 8. (a) Trend of the volume contraction (∆V %) as a function of the R3+ ionic radius (data point for Yb is an interpolated value); (b) values of the peritectic temperature, Tf, measured for the R3Pd5 (full circles) along with the literature data given for the formation of the “R2Pd3” phases (empty circles), plotted vs. the R3+ ionic radius. The dashed line is an eye-trace. 156x224mm (300 x 300 DPI)


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Figure 9. Updated version of the binary Gd-Pd (a) and Ho-Pd (b) phase diagrams. 413x624mm (72 x 72 DPI)



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Figure 10. Trend of the volume contraction (∆V %) vs. the peritectic temperature, Tf, for the R3Pd5 compounds (either determined in this work or literature data for the “R2Pd3”). The dashed line is the fit to a cubic function. 85x66mm (300 x 300 DPI)


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Figure 11. DC magnetic susceptibility, χ(T), vs. temperature measured between 2 and 300 K and at 3 kOe for Tb3Pd5 (a), Dy3Pd5 (b), Ho3Pd5 (c) and Er3Pd5 (d). The insets show the susceptibility on enlarged scale (data recorded at 180 Oe for Er3Pd5). 279x849mm (300 x 300 DPI)



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Figure 12. Inverse magnetic susceptibility, 1/χ(T), measured between 2 and 300 K and at 3 kOe for Tb3Pd5 (a), Dy3Pd5 (b), Ho3Pd5 (c) and Er3Pd5 (d); the straight line is the fit to the Curie-Weiss law. 279x857mm (300 x 300 DPI)


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Figure 13. The Néel temperatures, TN1 and TN2, of the R3Pd5 compounds with R = Tb, Dy, Ho and Er plotted vs. the R atomic number, Z(R), (the dashed lines are a trace to the eye) (a), and vs. the de Gennes factor (the solid lines are least-squares fits; the dashed lines are a linear extrapolation to obtain estimated values for Gd3Pd5) (b). 171x268mm (300 x 300 DPI)



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Figure 14. Isothermal magnetization, M(H), up to 140 kOe, measured at 2, 5, 10 and 15 K for Tb3Pd5 (a), at 2 K and 5 K for Dy3Pd5 (b), at 2, 5, 10 and 15 K for Ho3Pd5 (c) and at 2, 3.5 and 6 K for Er3Pd5 (d). The insets show the data between 0 and 20 kOe (0-40 kOe for Dy3Pd5). 279x812mm (300 x 300 DPI)


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Figure 15. Zero field heat capacity, CP, vs. temperature for Y3Pd5, Tb3Pd5 and Dy3Pd5 in the range 2-20 K (a) and Ho3Pd5 and Er3Pd5 in the range 2-14 K (b). 175x279mm (300 x 300 DPI)



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Figure 16. Entropy S4f as a function of temperature in Tb3Pd5, Dy3Pd5 and Er3Pd5 compounds. 87x69mm (300 x 300 DPI)


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Figure 17. Zero field electrical resistivity, ρ(T), of Y3Pd5, Tb3Pd5, Ho3Pd5 and Er3Pd5 between 2 and 300 K. 89x72mm (300 x 300 DPI)



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Figure 18. Electrical resistivity, ρ(T), of Y3Pd5, Tb3Pd5 and Ho3Pd5 between 2 and 40 K (a) and in-field electrical resistivity of Er3Pd5 between 2 and 10 K measured at several applied magnetic fields (b). 184x308mm (300 x 300 DPI)


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Figure 19. (a) Total and projected DOS curves for Y3Pd5 (Y in red, Pd in violet, total in black); (b) spin polarized total and projected DOS curves for Gd3Pd5 for an AFM spin ordering model (Gd in red and orange, Pd in violet and green, total in black). The Fermi levels are represented by dashed lines. 301x461mm (72 x 72 DPI)



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Graphical abstract. Coordination polyhedra surrounding the two in-equivalent rare earth atoms, R1 and R2, in the unit cell of the orthorhombic Pu3Pd5-type R3Pd5 compounds, along with the trend of the Néel temperatures, TN1 and TN2, plotted vs. the de Gennes factor. 797x356mm (72 x 72 DPI)


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Compounds (R = Sc, Y, GdâLu) - American Chemical Society

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Compounds (R = Sc, Y, GdâLu) - American Chemical Society