Synthesis and Characterization of Three New Layered Vanadium

Jan 14, 2016 - Synopsis. Three novel layered vanadium tellurites, MVTe2O8 (M = Al, Ga, and Mn), were synthesized and characterized. MnVTe2O8 reveals a...
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Synthesis and Characterization of Three New Layered Vanadium Tellurites, MVTe2O8 (M = Al, Ga, and Mn): Three-Dimensional (3-D) Antiferromagnetic Behavior of MnVTe2O8 with a Zigzag S = 2 Spin Chain Su-whan Bae,† Jisun Yoo,‡ Suheon Lee,§ Kwang Yong Choi,§ and Kang Min Ok*,† †

Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Republic of Korea Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States § Department of Physics, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Republic of Korea ‡

S Supporting Information *

ABSTRACT: Three new metal vanadium tellurites, MVTe2O8 (M = Al, Ga, and Mn) have been synthesized through standard solid-state and hydrothermal reactions. Crystal structure analyses using X-ray diffraction reveal that the isostructural materials exhibit layered structures consisting of MO6, TeO4, and VO4 polyhedra. The corner-sharing of MO6 octahedra results in one-dimensional (1-D) zigzag chains that are further interconnected by tetrameric Te4O12 units and the VO4 tetrahedra to complete a layered structure. Detailed structural analysis suggests that the unit-cell volumes and the very long Te(2)−O(2) bond distances in MVTe2O8 are closely related to the ionic radii of M3+ cations. Additional characterizations such as ultraviolet−visible light (UV-vis) and infrared spectroscopies, thermogravimetric analyses, and electron paramagnetic resonance measurements were performed. The temperature-dependent magnetic susceptibility measurements on MnVTe2O8 suggest that the material behaves like a threedimensional (3-D) antiferromagnet with TN = 30 K, although the structure consists of a zigzag S = 2 spin chain.

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INTRODUCTION Functional metal oxides have attracted huge scientific and industrial attention, which can be attributed to their remarkably important applications in electronics, catalysts, and optical devices with several key characteristics, such as electric, magnetic, and nonlinear optical properties.1 The functionalities surely have been understood through the thorough structural analysis of the materials. It is indeed a continuous challenge for synthetic chemists to synthesize novel superior performing functional oxides and to elucidate the structure−property relationships. Functional noncentrosymmetric (NCS) metal oxides have been drawing special interest to the field of inorganic material chemistry, because of their intriguing properties, such as piezoelectricity, second-harmonic generation, pyroelectricity, and ferroelectricity.1b,2 In general, macroscopic NCS structures are found from materials that contain intrinsic asymmetric building blocks, of which their polarizations do not cancel. One of the most representative strategies to the synthesis of novel NCS oxides is combining both families of second-order Jahn−Teller (SOJT) distortive cations, i.e., d0 transition metal cations under octahedral coordination moieties (Ti4+, V5+, Mo6+, etc.) and stereochemically active lone pair cations (Sb3+, Te4+, I5+, etc.).2,3 Combinations of d10 transition metal cations and/or materials with asymmetric π-systems to © XXXX American Chemical Society

extended structures are other successfully proven approaches to the discovery of new NCS metal oxides.3a,4 Among many cations, V5+ can exhibit various coordination modes, ranging from 4-coordinate tetrahedral coordination environment to 6coordinate octahedral geometry. In addition, the cation reveals relatively large off-center distortion in VO6 octahedral coordination modes.5 In fact, many vanadates with a variety of transition, alkali, and alkaline-earth metal cations have revealed very interesting structural flexibilities.6 Another very attractive flexible cation that is found in many metal oxides is tellurite, i.e., Te4+ that can accommodate being 3-, 4-, and 5coordinated with oxide ligands. The existence of the lone pairs on Te4+ forces the cation to have unsymmetrical polyhedral units.7 Our efforts to develop novel oxides containing asymmetric polyhedra in the M3+−V5+−Te4+−oxide system led us to synthesize three new quaternary metal vanadium tellurites, MVTe2O8 (M = Al, Ga, and Mn). In this paper, phase-pure syntheses, structure determinations, and spectroscopic and thermal characterizations of the materials, along with dipole moment calculations, are reported. With MnVTe2O8, detailed magnetic properties are also presented. Received: December 1, 2015

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DOI: 10.1021/acs.inorgchem.5b02784 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

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EXPERIMENTAL SECTION

Table 2. Selected Bond Distances for AlVTe2O8 and GaVTe2O8

Reagents. Al2O3 (Merck, 90%), Ga2O3 (Alfa Aesar, 99.999%), Mn2O3 (Aldrich, 99%), VO2 (Alfa Aesar, 99%), V2O5 (Junsei, 99%), and TeO2 (Alfa Aesar, 99%) were used as received. Synthesis. Single crystals of MVTe2O8 (M = Al and Ga) were grown by hydrothermal reactions. A 0.064 g (6.3 × 10−4 mol) portion of Al2O3, 0.094 g (0.5 × 10−3 mol) of Ga2O3, 0.083 g (1.0 × 10−3 mol) of VO2, and 0.160 g (1.0 × 10−3 mol) of TeO2, along with 0.4 mL of HCl solution (36 wt %) and 4 mL of deionized water, were combined. The reaction mixtures were placed in Teflon-lined stainless steel autoclaves. The reactors were tightly sealed and heated to 230 °C, held for 4 days (200 °C for 3 days for GaVTe2O8), and cooled to room temperature at a rate of 6 °C h−1. After cooling, each product was recovered by filtration and washed thoroughly with deionized water. Brown colored crystals of AlVTe2O8 and GaVTe2O8 were obtained in 10% and 21% yields, respectively, based on TeO2 along with powdered sample of TeVO4.8 Phase-pure polycrystalline samples of AlVTe2O8, GaVTe2O8, and MnVTe2O8 were prepared through standard solidstate reactions. Stoichiometric amounts of starting materials, M2O3 (M = Al, Ga, and Mn), V2O5, and TeO2 were mixed and thoroughly ground with agate mortars and pestles. The respective reaction mixtures were transferred into fused-silica tubes, evacuated, and sealed under vacuum. Each sealed tube was heated at 250 °C for 5 h (370 °C for GaVTe2O8), and then further heated gradually to 550 °C (525 °C for GaVTe2O8 and 460 °C for MnVTe2O8) with several intermittent regrindings (once for AlVTe2O8, six times for GaVTe2O8, and twice for MnVTe2O8). The phase purities of the polycrystalline products were examined by powder X-ray diffraction (PXRD), and the results were in good agreement with the calculated patterns from the singlecrystal X-ray diffraction (XRD) data. X-ray Diffraction. Single-crystal XRD was utilized to determine the crystal structures of AlVTe2O8 and GaVTe2O8. A brown plate (0.002 mm × 0.009 mm × 0.016 mm) for AlVTe2O8 and a brown plate crystal (0.007 mm × 0.014 mm × 0.042 mm) for GaVTe2O8 were used for the analyses. All the diffraction data were collected at room temperature with the scan widths of 0.30° and the exposure time of 10 s/frame. Graphite-monochromated Mo Kα radiation was used to snap diffraction images of respective crystals with a Bruker SMART BREEZE diffractometer with a 1K CCD area detector. The data were integrated using the SAINT program.9 The intensities of the data were corrected for polarization, absorption, and Lorentz factor. An absorption correction was applied on the data with the program SADABS.10 The crystal structures were solved and refined by SHELXS-97 11 and SHELXL-97,12 respectively. All calculation procedures were carried out using the software package WinGX98.13 Crystallographic data and selected bond distances of AlVTe2O8 and GaVTe2O8 are listed in Tables 1 and 2. PXRD was used by a diffractometer (Bruker, Model D8 Advance) at room temperature with

AlVTe2O8

AlVTe2O8

GaVTe2O8

461.12 P21/n 7.9351(10) 4.8413(7) 16.342(2) 93.720(10) 626.48(14) 4 298.0(2) 0.71073 4.889 0.0389 0.0567

503.86 P21/n 7.9198(2) 4.91690(10) 16.4311(4) 93.816(2) 638.42(3) 4 298.0(2) 0.71073 5.242 0.0242 0.0547

R(F) = ∑ ∥Fo| − |Fc∥/∑ |Fo|. ∑w(Fo2)2]1/2.

a

b

atom pairing

bond length (Å)

atom pairing

bond length (Å)

Al(1)−O(1) Al(1)−O(2) Al(1)−O(3) Al(1)−O(4) Al(1)−O(4) Al(1)−O(5) V(1)−O(3) V(1)−O(5) V(1)−O(7) V(1)−O(8) Te(1)−O(1) Te(1)−O(3) Te(1)−O(4) Te(1)−O(6) Te(2)−O(2) Te(2)−O(2) Te(2)−O(6) Te(2)−O(7)

1.815(8) 1.954(7) 1.929(8) 1.990(7) 2.031(7) 1.925(7) 1.791(7) 1.693(7) 1.826(7) 1.609(7) 1.864(7) 2.112(7) 1.939(7) 2.056(7) 1.872(6) 2.622(7) 1.897(6) 1.903(7)

Ga(1)−O(1) Ga(1)−O(2) Ga(1)−O(3) Ga(1)−O(4) Ga(1)−O(4) Ga(1)−O(5) V(1)−O(3) V(1)−O(5) V(1)−O(7) V(1)−O(8) Te(1)−O(1) Te(1)−O(3) Te(1)−O(4) Te(1)−O(6) Te(2)−O(2) Te(2)−O(2) Te(2)−O(6) Te(2)−O(7)

1.873(4) 1.992(3) 1.994(4) 2.038(4) 2.071(3) 1.999(4) 1.802(4) 1.690(4) 1.827(3) 1.615(4) 1.867(4) 2.113(3) 1.930(4) 2.066(3) 1.878(4) 2.583(2) 1.901(4) 1.903(4)

40 kV and 40 mA using Cu Kα radiation. Phase purities for all the synthesized products were examined via PXRD analyses. Although we were not able to grow single crystals of MnVTe2O8, the structure of the MnVTe2O8 was refined via the Rietveld method with the GSAS program.14 The PXRD data for the detailed Rietveld refinement was obtained from 5° to 100° in the 2θ range with a step time of 4 s and a step size of 0.02°. The single-crystal structure of GaVTe2O8 was used as a starting model for the refinement. Refinement results and final Rietveld plot of MnVTe2O8 can be found from the Supporting Information. Infrared (IR) Spectroscopy. IR spectra were recorded on a Thermo Scientific Nicolet iS10 ATR-FTIR spectrometer in the 400− 4000 cm−1 spectral range. UV-vis Diffuse Reflectance Spectroscopy. UV−vis diffuse reflectance spectral data were measured on a Varian Cary 500 scan UV-vis-NIR spectrometer over a wavelength range of 200−2500 nm at room temperature. The Kubelka−Munk Function was used to transform the obtained reflectance spectra to absorbance data.15 Thermogravimetric Analysis (TGA). SCINCO TGA N-1000 was used to obtain TGA diagrams for the reported materials. The samples were loaded in alumina crucibles and heated to 900 °C at a rate of 10 °C min−1 under flowing argon. Scanning Electron Microscopy/Energy-Dispersive X-ray Analysis (SEM/EDX). SEM/EDX has been carried out using a Hitachi S-3400N system and a Horiba Energy EX-250 instrument. EDX for AlVTe2O8, GaVTe2O8, and MnVTe2O8 reveal approximate M:V:Te ratios of 1.1:1.0:2.0, 1.0:1.0:1.7, and 1.0:1.0:2.0, respectively. Electron Paramagnetic Resonance (EPR) Measurements. Electron paramagnetic resonance (EPR) experiments were performed by using a commercial X-band spectrometer (JEOL, Model JESFA200) at room temperature at a frequency of 9.4411 GHz. Static Magnetization Measurements. Isothermal magnetization curve and temperature dependence of magnetic susceptibility of MnVTe2O8 crystals were measured using Quantum Design Magnetic Property Measurement System (MPMS) SQUID magnetometer in a field range of −7−7 T at 2 K and at an external field of 50 Oe in a temperature range of 2−300 K.

Table 1. Crystallographic Data for AlVTe2O8 and GaVTe2O8 fw space group a (Å) b (Å) c (Å) β (deg) V (Å3) Z T (K) λ (Å) ρcalcd (g cm−3) R(F)a Rw(F02)b

GaVTe2O8

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RESULTS AND DISCUSSION Structures. All the reported compounds are crystallizing in the centrosymmetric space group, P21/n. The isostructural compounds reveal very similar structures to that of previously reported material, InVTe2O8.16 Thus, only the structure of

Rw(F02) = [∑w(Fo2 − Fc2)2/ B

DOI: 10.1021/acs.inorgchem.5b02784 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry GaVTe2O8 that is in the Ga3+−V5+−Te4+−oxide system will be fully described here. GaVTe2O8 consists of GaO6 octahedra, VO4 tetrahedra, and TeO4 polyhedra with two different coordination environments (see Figure 1). The unique Ga3+

ionic radii of M3+ increase. However, the bond distances between Te(2) and O(2) in MVTe2O8 decrease as greater M3+ cations exist in the framework (see Figure 2a). It is obvious that the larger M3+ metal cations occupy the greater MO6 octahedral coordination environments, which results in the shorter Te(2)−O bond distances (see Figure 2b). In fact, the anisotropic change of unit-cell parameters for MVTe2O8 is consistent with the length change of Te(2)−O bonds that are pointing toward the approximate a-direction. The GaO6 octahedra share their corners through O atoms and form 1-D zigzag chains that are parallel to the b-axis (see Figure 3a). Also, the corner sharing of Te(1)O4 and Te(2)O4 polyhedra results in Te2O7 dimers. Further edge sharing of Te2O7 dimers through O(2) forms Te4O12 tetramers (see Figure 3b). Interconnections of the 1-D GaO6 zigzag chains, the tetrameric Te4O12 units, and the VO4 tetrahedra generate the layered structure (see Figure 3). Infrared Spectroscopy. The M−O (M = Al, Ga, or Fe), V−O, and Te−O vibrations are observed in infrared (IR) spectra. The bands occurring at ca. 415−522 cm−1, 421−544 cm−1, and 433−534 cm−1 can be assigned as Al−O, Ga−O, and Mn−O vibrations, respectively. The peaks found at ca. 850− 960 cm−1 and 700−800 cm−1 are attributable to VO and V− O vibrations. Multiple peaks found at ∼560−780 cm−1 can be assigned to Te−O vibrations. The assignments are in good agreement with those previously reported materials.16,20 Ultraviolet−Visible Light (UV-vis) Diffuse Reflectance Spectroscopy. The UV-vis diffuse reflectance spectral data of AlVTe2O8, GaVTe2O8, and MnVTe2O8 have been obtained. Kubelka−Munk function15 was used to calculate the K/S data. Approximate band gap energies were calculated to be 2.9, 3.0, and 1.9 eV for AlVTe2O8, GaVTe2O8, and MnVTe2O8, respectively, by extrapolating the linear part of K/S vs E plots (see Figure 4). The gaps and the visible absorption found for the reported compounds may be attributed to the degree of V(3d) orbitals in the conduction bands, as well as charge transfer in the vanadyl groups. Thermogravimetric Analyses (TGA). Thermogravimetric analysis (TGA) has been performed to study the thermal properties of the reported compounds. With AlVTe2O8 and GaVTe2O8, no weight loss has been observed up to 750 °C. With MnVTe2O8, however, a weight loss has been monitored at ca. 600 °C from the TGA diagram. In order to confirm the thermal behaviors of the materials, PXRD has been utilized after heating the samples to higher temperatures. On the basis of PXRD patterns, while the framework of AlVTe2O8 is thermally stable up to 400 °C, those for GaVTe2O8 and MnVTe2O8 are stable up to 500 °C. Further heating suggested that all of the compounds decomposed to M2TeO6 (M = Al, Ga, or Mn). Finally, PXRD data for the samples heated to 1000 °C revealed patterns of Al2O3 (Joint Committee on Powder Difraction Standards (JCPDS) Powder Diffraction File (PDF) Card No. 00-011-0661), V2O5 (PDF Card No. 00-041-1426), and Al2TeO6 (PDF Card No. 00-015-0689) for AlVTe2O8, Ga2O3 (PDF Card No. 00-056-1272), V2O5 (PDF Card No. 01-086-2248), Ga2TeO6 (PDF Card No. 01-082-2184) and unknown phase for GaVTe2O8, and Mn2V2O7 (PDF Card No. 00-022-0436) for MnVTe2O8. TGA diagrams and PXRD patterns measured at different temperatures for all three samples are found in the Supporting Information. Out-of-Center Distortions and Dipole Moment Calculations. The magnitude of out-of-center distortions (Δd) for MO6 (M = Al, Ga, or Mn) octahedra were calculated using the

Figure 1. ORTEP (50% probability ellipsoids) drawing exhibiting GaO6, VO4, and TeO4 polyhedra in GaVTe2O6.

cation is surrounded by six O2− ligands and forms a slightly distorted octahedron. The Ga−O bond lengths and the O−Ga−O bond angles range 1.873(4)−2.071(3) Å and 77.20(14)−177.47(14)°, respectively. The V5+ cation is coordinated by four oxide ligands in a distorted tetrahedral environment, where two V−O bond lengths [1.615(4) and 1.690(4) Å] are significantly shorter than other two V−O bond distances [1.802(4) and 1.827(3) Å]. The O−V−O bond angles in the VO4 tetrahedron range from 106.20(18)° to 112.12(19)°. Although both of the unique Te4+ cations form asymmetric polyhedra with oxide ligands, they have different coordination environments. While the Te(1)4+ cation shows two short [1.867(4) and 1.930(4) Å] and two long [2.066(3) and 2.113(3) Å] Te−O bond lengths in a seesaw moiety, the Te(2)4+ cation exhibits three short [1.878(4)−1.903(4) Å] and one very long [2.583(4) Å] Te−O bonds. Similar three short and one very long Te−O bonds suggesting the flexibility of TeO4 polyhedra have been observed from several tellurites.7b,17 The O−Te−O angles range from 77.58(14)° to 165.18(15)°. Because of the existing stereoactive lone pairs, all Te4+ cations are in an unsymmetrical environment. The structure of GaVTe 2 O 8 can be written as a neutral backbone of {[GaO2/3O4/3]−1.667 [VO2/2O1/3O1/1]+0.333 2[TeO2/2O2/3]+0.667}0 in connectivity terms. Bond valence sum calculations18 on GaVTe2O8 reveal values of 2.94, 4.77, 3.79− 3.87, and 1.68−2.20 for Ga3+, V5+, Te4+, and O2−, respectively. It should be noted that the volumes and the very long Te(2)− O(2) bond lengths in MVTe2O8 are closely related to the ionic radii of M3+ cations. The ionic radii for six-coordinate Al3+, Ga3+, and In3+ are 0.535, 0.62, and 0.8 Å, respectively.19 As can be seen in Figure 2a, the volumes of MVTe2O8 increase as the C

DOI: 10.1021/acs.inorgchem.5b02784 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 2. (a) Variation of the volumes and the very long Te(2)−O(2) bond distances as a function of the ionic radii of MVTe2O8 (M = Al, Ga, and In). (b) Ball-and-stick representation revealing how the Te(2)−O(2) bond lengths change as the coordination environment of MO6 varies.

previously reported methodology.21 The Δd values for MO6 in AlVTe2O8, GaVTe2O8, and MnVTe2O8 are calculated to be 0.26, 0.25, and 0.25, respectively, in which all the M3+ cations are classified as weak distorters. Considering the reported Δd for InVTe2O8 is 0.18,16 the out-of-center distortions of M3+O6 may be influenced by the cation sizes within the frameworks. The distortions for TeO4 polyhedra have been also determined via the dipole moment calculations in order to better understand the local asymmetric coordination moieties.22 The calculated dipole moments for TeO4 polyhedra in the compounds are ∼8.1−11.7 D (see Table 3). The values are consistent with those previously reported materials.23 EPR Measurements. To obtain information about crystal environments of Mn3+ ions, the EPR spectrum of the polycrystalline MnVTe2O8 sample was measured at a frequency of 9.4411 GHz and at T = 295 K. We observe a single EPR absorption line, which is well-fitted by a single Lorentzian profile (see the solid line in Figure 5). No additional sharp peaks related to impurities or structural defects are detectable, guaranteeing a high purity of the sample. The g-factor is calculated to be g = 1.99(8), which is typical for a high-spin state of Mn3+ (d4; S = 2) ions in an octahedral environment.24 In addition, a Lorentzian line shape implies the presence of an exchange interaction between Mn3+ ions, leading to a narrowing of the EPR signal through fast electronic fluctuations

of Mn3+ ions. The narrow line width of 50.2 mT is mainly due to exchange anisotropies since a single ion anisotropy of Mn3+ is negligible. Static Magnetization Measurements. The temperature dependence of the magnetic susceptibility, χ(T), was measured for MnVTe2O8 at T = 2−300 K under an external field of H = 50 Oe. The results of the MnVTe2O8 powder sample are presented in Figure 6a. As evident from the inverse susceptibility in Figure 6b, χ(T) follows the Curie−Weiss law for temperatures above 80 K: χ (T ) =

C + χ0 T − ΘCW

where C, ΘCW, and χ0 are the Curie constant, the Curie−Weiss temperature, and the constant terms arising from the diamagnetism of the core electron shells and the van Vleck paramagnetism of the open shells of the Mn 3+ ions, respectively. The fit yields C = 3.10(2) mol−1 K, ΘCW = −58.7(9) K, and χ0 = 3.12(9) × 10−4 emu/mol Oe. The effective magnetic moment is estimated to μeff = 4.97 μB, which is slightly larger than the spin-only value of μtheor = 4.89 μB per Mn3+. The sizable negative value of ΘCW indicates a moderate antiferromagnetic coupling between the Mn3+ ions. According to the crystal structure, MnVTe2O8 realizes a zigzag S = 2 spin chain, in which the Mn3+ ions are coupled to D

DOI: 10.1021/acs.inorgchem.5b02784 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 3. Wire models representing (a) 1-D zigzag chains of the corner-shared GaO6 octahedra, (b) Te4O12 tetramers, (c) VO4 tetrahedra, (d) one layer in the bc-plane, and (e) complete layered structure of GaVTe2O8 in the ac-plane.

Figure 5. Derivative of the EPR spectrum measured at T = 295 K and at a frequency of 9.4411 GHz. Figure 4. UV-vis spectra of MVTe2O8 (M = Al, Ga, and Mn).

each other via Mn−O−Mn exchange path. In mean-field approximation, the nearest neighbor intrachain interaction (J) is given by

Table 3. Calculation of Dipole Moments for TeO4 Polyhedra

a

compound

TeO4

dipole moment (D)a

AlVTe2O8

Te(1)O4 Te(2)O4

8.6 11.7

GaVTe2O8

Te(1)O4 Te(2)O4

8.7 11.5

MnVTe2O8

Te(1)O4 Te(2)O4

8.1 11.2

J=−

3ΘkB = 14.7 K zJ(J + 1)

where z is the number of nearest neighbors (z = 2) and kB is the Boltzmann constant. However, the anticipated broad maximum for an antiferromagnetic spin chain is lacking. Instead, there appears a rather sharp maximum at ∼38 K, with a subsequent low-temperature upturn. This feature indicates a 3D network of S = 2 spins due to considerable interchain interactions. Indeed, there are longer-range superexchange

D = Debyes.

E

DOI: 10.1021/acs.inorgchem.5b02784 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 6. (a) Temperature dependence of the magnetic susceptibility of MnVTe2O8 (open circles) measured in an applied magnetic field of 50 Oe. The dotted line is a defect contribution and the solid line is an intrinsic susceptibility. The inset shows a derivative dχintrinsic(T)/dT. The magnetic transition temperature is marked by the vertical arrow. (b) Temperature dependence of the inverse susceptibility with a fit to the Curie−Weiss law (solid line). (c) Magnetization versus field measured at T = 2 K. The solid lines are a linear fit.

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paths Mn−O−Te−O−Mn between the interchain Mn3+ ions, although the distance between them is rather long. To obtain the intrinsic susceptibility, the low-temperature upturn is fitted to the Curie−Weiss susceptibility of defect spins, χdefect(T) = C/(T − ΘCW). The defect spins amount to 1.5% of the total Mn3+ spins. After the subtraction of the defect contribution, we obtain the intrinsic magnetic susceptibility, which features 2/3 of the maximum susceptibility value at zero temperature (see the solid line in Figure 6). We are able to identify a long-range magnetic interaction from the lambda-like peak at TN = 30 K in the derivative dχintrinsic(T)/dT, as shown in the inset of Figure 6a. Isothermal magnetization curve M(H) was measured at 2 K in a field range from −7 T to 7 T (see Figure 6c). M(H) increases quasi-linearly as the field increases. The magnetization is expected to reach a saturated magnetic moment of Ms = 4.97 μB at ∼90 T. Extrapolating the linear fit in the positive and negative field shows a small offset. This is attributed to a spinflop transition, lending further support to the antiferromagnetic ordering.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.5b02784. Experimental and calculated PXRD patterns, final Rietveld plot, TGA diagrams, and IR spectra for MVTe2O8 (M = Al, Ga, and Mn) (PDF) X-ray crystallographic file for MVTe2O8 (M = Al and Ga) (CIF)

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +82-2-820-5197. Fax: +82-2-825-4736. E-mail: kmok@ cau.ac.kr. Funding

Funding provided by National Research Foundation of Korea (NRF) (Grant No. 2013R1A2A2A01007170). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This research was supported by the National Research Foundation of Korea (NRF) funded by Ministry of Science, ICT and Future Planning (Grant No. 2013R1A2A2A01007170).

CONCLUSIONS

Single crystals and pure polycrystalline samples of three new transition-metal vanadium tellurites, MVTe2O8 (M = Al, Ga, and Mn) have been prepared. The isostructural materials reveal layered structures that consist of MO6, VO4, and TeO4 polyhedra. The materials also have been thoroughly characterized through infrared (IR) and ultraviolet−visible light (UVvis) diffuse reflectance spectroscopies, along with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) and TGA analyses. Out-of-center distortions and dipole moment calculations for the reported materials have been successfully presented. The magnetic behavior of MnVTe2O8 turns out to be a three-dimensional antiferromagnet with TN = 30 K, although its structure constitutes a zigzag S = 2 spin chain.

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REFERENCES

(1) (a) Fierro, J. L. G.; Taylor & Francis: Boca Raton, FL, 2006;. (b) Bruce, D. W.; O’Hare, D.; Walton, R. I.; Wiley: Chichester, UK, 2010. (2) Halasyamani, P. S.; Poeppelmeier, K. R. Chem. Mater. 1998, 10, 2753−2769. (3) (a) Jiang, H.; Kong, F.; Fan, Y.; Mao, J.-G. Inorg. Chem. 2008, 47, 7430−7437. (b) Oh, S.-J.; Lee, D. W.; Ok, K. M. Inorg. Chem. 2012, 51, 5393−5399. (4) (a) Wu, Y. C.; Sasaki, T.; Nakai, S.; Yokotani, A.; Tang, H. G.; Chen, C. T. Appl. Phys. Lett. 1993, 62, 2614−2615. (b) Chen, C. T.; Ye, N.; Lin, J.; Jiang, J.; Zeng, W. R.; Wu, B. C. Adv. Mater. 1999, 11, F

DOI: 10.1021/acs.inorgchem.5b02784 Inorg. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.inorgchem.5b02784 Inorg. Chem. XXXX, XXX, XXX−XXX