Structure, Superconductivity, and Magnetism of Ce(O,F)BiS2 Single

Nov 20, 2014 - Their properties are likely related to the minor structural change even if F contents in the crystals were not significantly different...
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Structure, Superconductivity, and Magnetism of Ce(O,F)BiS2 Single Crystals Published as part of the Crystal Growth & Design virtual special issue on Anion-Controlled New Inorganic Materials Akira Miura,*,#,†,⊥ Masanori Nagao,*,#,†,‡ Takahiro Takei,† Satoshi Watauchi,† Yoshikazu Mizuguchi,‡,§ Yoshihiko Takano,‡ Isao Tanaka,† and Nobuhiro Kumada† †

Center for Crystal Science and Technology, University of Yamanashi, 7-32 Miyamae, Kofu 400-8511, Japan National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan § Department of Electrical and Electronic Engineering, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo 192-0397, Japan ‡

S Supporting Information *

ABSTRACT: The crystal structures of Ce(O,F)BiS2 synthesized from starting materials with five different F contents were determined by single-crystal X-ray analysis. An increase in F content in the starting materials slightly increased F incorporation in the grown single crystals. The grown crystals with various F contents showed similar layered structures, but minor structural changes were observed with different conductive and magnetic properties. Crystals grown from higher F content were found to have a nearly flat Bi−S plane and elongated Ce− (O,F) bond, and showed superconductive transition below ∼3 K and spontaneous magnetization below ∼7 K. The calculated density of states based on this structural analysis predicted that hybridized Bi 6p−S 3p orbitals intersect the Fermi level and that Ce states are located near the Fermi level. The effect of structural change on superconductivity and longrange magnetic ordering has been discussed.

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magnetic-like properties.6−10 Magnetic ordering in La(O,F)BiS2, Pr(O,F)BiS2, and Nd(O,F)BiS2 has not been reported thus far, suggesting that the magnetic ordering in Ce(O,F)BiS2 can be attributed to the Ce(O,F) layers. Computational calculations have also predicted ferromagnetic ordering in Ce(O,F)BiS2 to be thermodynamically stable.7 However, there is some discrepancy in the literature regarding the magnetic properties of these complexes. Yazici et al. reported the superconductivity of CeO0.5F0.5BiS2 powder at ∼2 K and possible magnetic ordering at low temperature.6 Xiang et al. systematically investigated a series of CeOxF1−xBiS2 powders and reported correlations between F content and lattice parameters, resistivity, and magnetic properties.8 They argued that superconductivity appears with the semiconducting normal state of the F dopant when x > 0.25, and that ferromagnetismlike ordering occurs at x = 0 and 0.5 at the magnetic transition temperature (Tm) of ∼5 K. Superconductivity and ferromagnetic-like ordering in CeOxF1−xBiS2 (x ≈ 0.5) have been confirmed by Jha and Awana, who also used powder samples.9 Demura et al. investigated CeOxF1−xBiS2 powders with systematic variations in F content and suggested the

INTRODUCTION Layered materials have received considerable attention in recent years, as layers with different components and properties can be stacked together to prepare structures with anisotropic properties. For example, high-temperature superconductors are highly attractive layered materials consisting of both superconducting and blocking layers.1 The stacking components and sequence, as well as the statistical substitution and/or defects, significantly affect the superconductive properties, though the superconductivity mechanism is still under debate. Twodimensional materials in which long-range magnetic ordering exists within or between layers are also of interest.2 Ru-based layered materials, such as RuSr2Ln2Cu2O10 and RuSr2LnCu2O8 (Ln: Ce, Eu, Gd, Sm) complexes, consist of a superconductive CuO layer and a magnetic RuO layer.3 Investigation of such materials could provide the key to the relationship between superconductivity and magnetism, facilitating the development of new multifunctional materials. Recently, mixed anion compounds, whose properties can be tuned by incorporating different anions, have received considerable interest.4 Ln(O,F)BiS2 (Ln: La, Ce, Pr, Nd, Yb) complexes constitute a class of layered mixed-anion superconductors with structures consisting of BiS2 conductive planes and Ln(O,F) blocking slabs.5,6 Of this class of complexes, Ce(O,F)BiS2 has exhibited both superconductive and ferro© XXXX American Chemical Society

Received: April 15, 2014 Revised: October 20, 2014

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Table 1. Summary of F/(O+F) Ratio, Room-Temperature Structural Parameters, and Transition Temperatures of Superconductivity and Long-Range Magnetic Ordering in Ce(O,F)BiS2 Single Crystalsa Crystal

Crystal 1

Crystal 2

Crystal 3

Crystal 4

Crystal 5

ratio of F/(O+F): starting material ratio of F/(O+F): grown crystal a/Å c/Å volume/Å3 Bi−S(1) [interplane] × 4/Å S(1)−Bi−S(1)[interplane] /deg Bi−S(2) /Å S(1)−Bi−S(2) /deg Ce−(O,F) × 4/Å Ce−(O,F)−Ce /deg Ce−S2 × 4/Å S2−Ce−S2 /deg S2−Ce−(O,F) /deg residuals: R (I > 2.00(I)) residuals: wR2 (reflections) goodness of Fit Indicator Tc (zero resistivity)/K Tc (Meissner effect)/K Tm (magnetic ordering)/K

0.3 0.53(5) 4.019(3) 13.507(5) 218.2(3) 2.843(2) 177.1(4) 2.507(8) 91.4(2) 2.3826(18) 115.00(10) 3.110(4) 80.50(12) 70.93(13) 0.045 0.091 1.03

0.5 0.61(5) 4.031(3) 13.383(5) 217.5(3) 2.850(2) 179.3(3) 2.517(7) 90.36(16) 2.4044(16) 113.77(9) 3.096(3) 81.25(10) 70.55(11) 0.034 0.075 1.03 2.9(1) 2.7(3) 5.1(4)

0.7 0.65(5) 4.026(3) 13.340(5) 216.2(3) 2.847(2) 180.1(3) 2.529(6) 89.97(16) 2.4048(16) 113.67(9) 3.082(3) 81.57(9) 70.29(9) 0.034 0.084 1.16 3.2(1) 3.0(2) 5.6(1)

0.8 0.64(5) 4.031(3) 13.338(5) 216.7(3) 2.850(2) 180.4(4) 2.526(8) 89.8(2) 2.4098(17) 113.52(9) 3.085(4) 81.57(12) 70.34(13) 0.043 0.084 1.08 3.0(1) 3.1(1) 6.0(1)

0.9 0.66(5) 4.030(3) 13.336(5) 216.6(3) 2.850(2) 180.4(4) 2.537(7) 89.80(19) 2.4112(16) 113.37(9) 3.079(3) 81.74(10) 70.20(11) 0.041 0.077 1.19 3.0(1) 3.1(1) 7.1(1)

a Tc (zero resistivity) and Tc (Meissner effect) are defined as the highest temperature at which resistivity falls below 0.1 μΩ cm−1 and by the onset temperature at which zero-field cooled (ZFC) curve starts to drop, respectively. Tm was determined as the temperature at which the ZFC curve begins to deviate from the field cooled (FC) curve.

samples, it is important to further examine the structural and property detail in single crystal analysis. In the present study, we report the structure, superconductivity, and magnetic properties of five different Ce(O,F)BiS2 single crystals prepared from starting materials with different F content. Changes in the F/(O+F) ratio of the starting materials caused slight alterations in the crystallographic structures of the grown Ce(O,F)BiS2 single crystals. Even though the F content of the resulting crystals was similar, both the superconductivity and magnetic ordering of the crystals were sensitive to the small changes to the crystal structure brought about by changes in the F concentration of the starting material.

coexistence of superconductivity and ferromagnetic-like properties.10 The superconductive transition temperature (Tc) was 2− 3 K in the powder samples; however, in contrast to the report by Xiang et al.,8 magnetic ordering was observed only above x ≈ 0.4. In addition, a higher Tm of ∼7.5 K was reported for heavily doped samples. High-pressure annealing increased Tc up to ∼7 K, while it did not significantly alter Tm. Therefore, although the existence of both superconductivity and magnetic ordering in mixed anion compounds has been observed by different groups, the values reported for these properties differ. This may be attributed to the inhomogeneity of powder samples or the effects of impurity phases and grain boundaries in sample characterization. Single crystal growth and structural analysis of CeOBiS2 without F dopants was reported some decades ago.11,12 Recently, we reported the growth of Ln(O,F)BiS2 single crystals (Ln: La, Ce, and Nd) with different F concentrations and the temperature dependence of their resistivity and magnetization.13,14 Together with superconductive properties, magnetic ordering was found in two kinds of Ce(O,F)BiS2 crystals prepared from starting materials with different F contents.14 Interestingly, even though the lattice parameter (c) and the detected F content of these two crystals were comparable, they exhibited different magnetic transition temperatures. Since the investigation of single crystals can reduce the effects of impurity phases and grain boundaries, further structural analysis would improve the understanding of the intrinsic nature of CeOxF1−xBiS2 and clarify how superconductivity and magnetic ordering appear. Very recently, Sugimoto and Paris et al. examined the powder samples by extended X-ray absorption fine structure (EXAFS) measurements, which revealed local structural change as well as the valence of Ce.15 They suggest that the increased Ce3+ component and suppression of the Ce−S−Bi compiling channel lead the coexistence of superconductivity and ferromagnetic-like behavior.15a As they use only powder

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EXPERIMENTAL AND COMPUTATIONAL METHODS

The growth of the single crystals discussed in this work has been described elsewhere.14 Briefly, five different crystals were produced from different ratios of Ce2S3, Bi, Bi2S3, Bi2O3, and BiF3. The nominal compositions of the starting materials were Ce(O0.7F0.3)BiS2 (Crystal 1), Ce(O0.5F0.5)BiS2 (Crystal 2), Ce(O0.3F0.7)BiS2 (Crystal 3), Ce(O0.2F0.8)BiS2 (Crystal 4), and Ce(O0.1F0.9)BiS2 (Crystal 5). The crystals were grown using CsCl-KCl flux at 600−800 °C. Subsequently, the CsCl-KCl flux was washed off with water, and plate-shaped crystals were collected. Compositional, structural, and physical property measurements were carried out as described in our previous reports.14 Chemical compositions were determined by electron probe microanalysis (EPMA). Crystallographic structures were determined by singlecrystal X-ray diffraction analysis using Rigaku XTALAB-MINI with graphite-monochromated MoKα radiation. Structural refinement was performed by SHELXL-9716 using the reported atomic position of La(O,F)BiS2 as initial models.17 The structural scheme was drawn by VESTA.18 Magnetization and transport properties were measured by a superconducting quantum interference device (SQUID) and a physical property measurement system (PPMS), respectively. B

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RESULTS All the grown crystals contained a chemical composition of Ce:Bi:S = 1.01:0.99:2. The F/(O+F) ratios were found to be 0.53 (Crystal 1), 0.61 (Crystal 2), 0.65 (Crystal 3), 0.64 (Crystal 4), and 0.66 (Crystal 5).14 The error in the EPMA analysis was approximately 5%. An increase in F content of the starting materials seemed to facilitate F incorporation in the grown crystals, although similar F content was observed between Crystals 3−5. The space group of all the crystals was P/4nmm. An increase in the F content of the starting materials produced a similar or slightly higher lattice constant along the a-axis but decreased the lattice constant along the c-axis, as shown in Table 1. This is consistent with several papers on Ln(O,F)BiS2 that discuss the shortening of the c-axis lattice parameter with an increase in the F content.5−10 However, while the lattice parameters along the c-axis decrease from Crystal 1 to Crystal 3, both the a- and caxes of Crystals 3−5 are comparable. For all the crystals, refinements revealed no defects in the Ce, S, and O/F sites. The occupancies of Bi are close to unity, but slight vacancies are possible. In this study, further structural refinements were performed with full occupancies for all sites. The final R values were 3−5%. More details of data collection and structural data are reported in the Supporting Information. The refined structure of Crystal 5, which was synthesized from the starting material with the highest F content, is shown in Figure 1. The structure can be seen as a stacking of BiS2 and CeO layers. Compared to nondoped CeOBiS2, the in-plane Bi−S(1) distance in Crystal 5 is similar to that of the nondoped crystal (2.84(2) Å),11 while the Ce−(O,F) bond distance is longer (2.370(5) Å).11 These bond distances are between those

of LaO1−xFxBiS2 (x ≈ 0.46)17 and NdO1−xFxBiS2 (x ≈ 0.3).13 The Bi−S(1) and Ln−(O,F) distances in the La complex are 2.8730(14) Å and 2.4338(13) Å, respectively; those of the Nd complex are 2.827(2) Å and 2.3704(17) Å, respectively. These differences can be partially attributed to the lanthanide contraction. Like La(O,F)BiS2 and Nd(O,F)BiS2 single crystals,13,17 the equivalent isotropic atomic displacement parameter (Beq) of S(1) in Crystal 5 is higher than that of S(2) (2.07(17) Å2 compared to 1.28(13) Å2). The designation of S(1) and S(2) is shown in Figure 1. A similar trend was found for all of the crystals. Figure 1 also shows a comparison between Crystal 1, which had lowest F content, and Crystal 5. While the increase in F content does not significantly affect the Bi−S(1) bond length, it does alter the S(1)−Bi−S(1) angle. In Crystal 5 this angle is nearly flat, whereas in Crystal 1 it is slightly zigzag. A similar zigzag plane is also found in CeOBiS2 (S−Bi−S: 177.1(4)°).11 These changes are consistent with the results of the single-crystal analysis of La(O,F)BiS2.17 The increase in F content elongates Bi−S(2) and Ce−(O,F) bond distances but shortens the Ce−S(2) distance. This trend agrees with the report about EXAFS analysis Ce(O,F)BiS2 in powder samples.15b The angles of Bi−S(2)−Ce, S(2)−Ce−(O,F), and Ce−(O,F)−Ce angle also change with increasing F content. Table 1 shows the structural parameters for Crystals 2−4, which are intermediate between those of Crystals 1 and 5. While the structural changes from Crystal 1 to 3 are clear by terms of lattice parameters and coordination of Bi and Ce while these parameters and coordination of Crystal 3−5 are similar. Crystal 1 contains a slightly zigzag Bi−S(1) layer, while the Bi− S(1) layer of Crystals 2 and 3 become nearly flat. The Bi−S(2), Ce−S(2), and Ce−(O,F) bonding also change from Crystal 1 and Crystal 3. In contrast, structural parameters of Crystals 3 and 4 are within experimental error of one another except the distance of the Ce−(O,F) bond. All of the structural parameters of Crystals 4 and 5 are comparable. Figure 2 shows the temperature dependence of the resistivity and magnetism for Crystals 1−5, between 2−10 K. In this temperature range, all resistivity were below a few mΩ cm−1. To emphasize the temperature dependence of the data, all measurements have been normalized to data acquired at 10 K.

Figure 1. Crystal structure of Ce(O,F)BiS2 (Crystal 5). Bond distances and angles are given in Å and degrees, respectively. Percentage values are derived from the values of Crystal 5 divided by those of Crystal 1, and plus/minus indicates expansion/shrinkage of Crystal 5 from Crystal 1.

Figure 2. Temperature dependence of resistivity (top) and magnetic susceptibilities (bottom) of Crystals 1−5.14 The resistivity values have been normalized to those acquired at 10 K. The temperature dependence of the magnetic susceptibilities of Crystals 1−5 was measured under an applied magnetic field of 10 Oe parallel to the abplane.

The density of states (DOS) of the Ce(O,F)BiS2 crystals was calculated using the VASP package.19 The GGA(PBE)+U approach was implemented,20 and spin polarization was considered for the calculations. The experimentally determined unit cells of Crystals 1 and 5 were used, and no structural optimization was performed. The kpoint 12 × 12 × 4 grids21 and an energy cutoff of 500 eV were used for the calculation. Antiferromagnetic and ferromagnetic orderings were chosen for Crystals 1 and 5, respectively, assuming the spin configuration reported in the literature.7

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ordering of Crystal 1 and FM ordering of Crystal 5, is shown in Figure 4. The contributions of Bi, S, O, and F were almost

Crystal 1 showed the possible onset of superconductive transition at ∼2.3 K, though zero resistivity was not confirmed. In contrast, Crystals 2−4 showed zero resistivity at ∼3 K. All of the crystals exhibited semiconductive behavior in the normal region, which was consistent with previous reports of Ce(O,F)BiS2 powders with different F contents.8,10 In the normal region, the conductivity of Crystal 1 showed relatively little temperature dependence. As the F content in the starting materials increased from Crystal 2 to Crystal 4, the temperature dependence decreased. Crystals 4 and 5 showed comparable conductivity behavior. The thermomagnetic (M−T) curve of Crystal 1 shows no clear transition (Figure 2, bottom). Crystals 2−5 show a decrease in magnetization around 3 K, which corresponds to the temperature of zero resistivity. Additionally, deviation between zero-field cooling (ZFC) and field cooling (FC) was found in Crystal 2 near 5 K, which suggests spontaneous magnetization. This deviation was enhanced, and its onset shifted to higher temperatures, with increasing F content; in Crystal 5, its onset was near ∼7 K. Figure 3 shows the isothermal M−H curve of Crystal 5 at 2 K. The hysteresis loop that was observed supports spontaneous

Figure 4. pDOS of CeO0.5F0.5BiS2 calculated by the GGA+U approach using the VASP code. Structures of Crystal 1 with AFM ordering and Crystal 5 with FM ordering are used for the calculations, which are shown on the left and right sides, respectively. The Fermi level is set to 0 eV.

independent of the U value. Near the Fermi level, hybridization of the Bi6p and S 3p orbitals was observed, in agreement with previous calculations of Ce(O0.5F0.5)BiS2.7 This result also agreed with calculations of Ln(O0.5F0.5)BiS2.7,22 The primary contributions of the Bi and S states were above −6 eV; those of the O and F states were near −5.5 and −9 eV, respectively. The location of the Ce states depended on the magnetic structure and the U value. While the states of the AFM configuration were nearly symmetric between up- and downspins, the states of the FM configuration were asymmetric. As the U value increased, the partial Ce states near the Fermi level separate into two: one near the Fermi level and the other below the Fermi level. These Ce states were mainly composed of 5d and 4f orbitals. There was some degree of overlap between the Ce, S, and O/F states over a wide energy range.

Figure 3. M−H curve of Crystal 5 at 2 K parallel to the ab-plane.

magnetization. The saturation magnetization was ca. 0.02 μB/ Ce, and this value that is much smaller than that expected for the Ce3+ free ion (2.54 μB/Ce). The value of Hc1 attributed to its superconductivity was 10−20 Oe. To understand the contributions and overlap of electron orbitals in Ce(O,F)BiS2 crystals, we calculated the partial density of states (pDOS) based on the experimentally determined crystal structures. A number of assumptions were made to simplify the calculations. A value of 1/2 was used for the F/(O+F) ratio, though this assumption underestimates the true F value. As the random occupancy of O and F was difficult to calculate, the ordered model was used. The GGA+U approach was used to simulate Ce orbital. As the U value cannot be determined by computational calculation alone, we performed calculations using three different values of U for Ce: 0, 2.5, and 5 eV. The antiferromagnetic (AFM) and ferromagnetic (FM) ordering of Ce were treated as separate calculations, though this approach may oversimplify the true magnetic structures. Although numerous assumptions have been made in our calculations, overall trends for these crystals can be estimated with a fair degree of accuracy. The pDOS was calculated using two structural models (Crystal 1 and 5), two magnetic structures, and three different U values. The valence band of the pDOS was considerably affected by the magnetic structure and the U values but was not significantly affected by the crystal structure (see Supporting Information). The pDOS of Ce(O0.5F0.5)BiS2, based on AFM

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DISCUSSION Crystallographic structural analysis was performed on five types of Ce(O,F)BiS2 single crystals grown from starting materials with different F contents. The structural parameters of these crystals were largely similar, though noticeable differences in lattice parameters, bond lengths, and angles were observed. Zero resistivity and magnetic ordering were observed in the crystals grown from starting materials with higher F concentrations. Thus, the F content available during crystal growth affects not only the crystallographic structure but also the physical properties. The F concentration of Crystal 1, grown under conditions with the lowest F content, was noticeably lower than that of Crystals 3−5, which exhibited little variability in F content. Thus, it appears the F content of the grown crystals can be altered by the F content of the growth conditions, though more sophisticated analyses will be required to determine the exact relationship between growth conditions and the F content of the crystals. Superconductivity and magnetic ordering were closely related to the crystal structures. Zero resistivity was confirmed when a nearly flat Bi−S plane was formed. The calculated pDOS suggests that the hybridized Bi6p and S 3p orbitals intersect the Fermi level and can thus be correlated to D

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conductivity. An increase in the flatness of the Bi−S plane would enhance overlap of the Bi 6p and S 3p orbitals. This enhanced overlap may be related to the occurrence of superconductivity, similar to the case of La(O,F)BiS2.17 Superconductive behavior may also be related to an increase in F concentration from Crystal 1 to Crystal 3. All of the Ce(O,F)BiS2 crystals exhibit semiconductive behavior. Even though the F concentration of Crystals 2−5 were comparable, in the normal region, the temperature dependence of resistivity decreased as the F content of the starting material increased. This may suggest a higher carrier concentration in the crystals grown under high F concentration due to enhanced F incorporation. Nonetheless, metallic behavior was not found in any of the crystals, in contrast to the metallic behavior of heavily F-doped La(O,F)BiS2 and Nd(O,F)BiS2 superconductive crystals.14,17 The reason for this is still unclear. Magnetic ordering was found only in the Ce(O,F)BiS2 crystals with higher F content in the starting materials, which agreed with the powder sample results reported by Demura et al.10 As single crystals of La(O,F)BiS2 and Nd(O,F)BiS2 do not show such spontaneous magnetization,14 the magnetic ordering in Ce(O,F)BiS2 can be attributed to Ce orbital. This assertion is supported by computational predictions. Magnetic ordering of Ce may be related with the change of crystal structure. Crystal 1 shows no magnetic ordering. Crystals 2 and 3 show enlarged Ce−(O,F) and Bi−S(2) bond lengths and shortened Ce−S(2) length with a similar Tm of ∼5 K. The angles of Bi−S(2)−Ce and Ce−(O,F)−Ce are also changed. The enlarged Ce−(O,F) length supports the partial reduction from Ce4+ to Ce3+, and the elongated bond length of Bi−S(2) can suppress Bi−S(2)− Ce coupling channel.15a We also note that the angle change of Bi−S(2)−Ce determined by single-crystal analysis shows the same trend as those predicted by EXAFS analysis.15 As suggested,15a the bonding of Bi−S(2)−Ce can derive the system from valence fluctuation regime to the Kondo-like regime, which can cause the magnetic ordering together with the superconductivity. The structural data of Crystal 3−5 are similar, but the Crystals 4 and 5 exhibit a further elongated Ce− (O,F) bond. Compared to 3, Crystals 4 and 5 exhibit increased Tm values, up to ∼7 K. The increase of magnetic-ordering temperature could be related to elongated Ce−(O,F) bond with weakened superexchange interactions. Nonetheless, we cannot deny the possibility that other slight changes within the experimental error also affects the magnetic property, considering comparable structures and different magnetic onsets of Crystals 4 and 5. Future studies should be performed to investigate the magnetic structure and valence of Ce and Bi by using single crystals, and larger single crystals should be grown for neutron diffraction study.

attributed to the suppression of Bi−S(2)−Ce coupling channel and/or elongated Ce−(O,F) bond with weakened superexchange interactions. Further challenges remain for a more accurate quantitative analysis of the F content of the crystals, their effect on the valences of Bi and Ce, the reasons for semiconductive behavior, and the magnetic structures of the crystals.

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ASSOCIATED CONTENT

S Supporting Information *

CIF data and detailed structural data of five Ce(O,F)BiS2 crystals and additional calculated density of states. These materials are available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*(A.M.) E-mail: [email protected]. *(M.N.) E-mail: [email protected]. Present Address ⊥

(A.M.) Hokkaido University Faculty of Engineering, Kita 13 Nishi 8, Kita-ku, Sapporo 060−8628, Japan.

Author Contributions #

A.M. and M.N. contributed equally.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS A.M. and M.N. thank Mr. Yuki Iguchi and Prof. Hiroshi Yanagi (University of Yamanashi) for preliminary experiments and discussions about density of states, and Prof. Yoichi Kamihara (Keio University) and Prof. Jun Akimitsu (Aoyama Gakuin University) for comments about magnetization, and Dr. XiaoDong Wen (Los Alamos National Laboratory) for comments about DFT calculations.

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REFERENCES

(1) (a) Bednorz, J. G.; Müller, K. A. Z. Phys. B Condens. Mater. 1986, 64 (2), 189−193. (b) Chu, C. W.; Gao, L.; Chen, F.; Huang, Z. J.; Meng, R. L.; Xue, Y. Y. Nature 1993, 365 (6444), 323−325. (c) Wu, M.; Ashburn, J.; Torng, C.; Hor, P.; Meng, R.; Gao, L.; Huang, Z.; Wang, Y.; Chu, C. Phys. Rev. Lett. 1987, 58 (9), 908−910. (d) Maeda, H.; Tanaka, Y.; Fukutomi, M.; Asano, T. Jpn. J. Appl. Phys. 1988, 2, L209−L210. (e) Takeshita, N.; Yamamoto, A.; Iyo, A.; Eisaki, H. J. Phys. Soc. Jpn. 2013, 82 (2), 023711. (2) (a) Kitagawa, S.; Ikeda, H.; Nakai, Y.; Hattori, T.; Ishida, K.; Kamihara, Y.; Hirano, M.; Hosono, H. Phys. Rev. Lett. 2011, 107, 27. (b) Miura, A.; Takei, T.; Kumada, N.; Magome, E.; Moriyoshi, C.; Kuroiwa, Y. J. Alloys Compd. 2014, 593, 154−157. (3) (a) Awana, V. P. S.; Karppinen, M.; Yamauchi, H. In Studies of High Temperature Superconductors; Narlikar, A. V., Ed.; Nova Sci. Publ.: New York, 2002; Vol. 46. (b) Nachtrab, T.; Bernhard, C.; Lin, C.; Koelle, D.; Kleiner, R. C. R. Phys. 2006, 7 (1), 68−85. (4) (a) Clarke, S. J.; Adamson, P.; Herkelrath, S. J. C.; Rutt, O. J.; Parker, D. R.; Pitcher, M. J.; Smura, C. F. Inorg. Chem. 2008, 47 (19), 8473−8486. (b) Tsujimoto, Y.; Yamaura, K.; Takayama-Muromachi, E. Appl. Sci. 2012, 2 (1), 206−219. (c) Attfield, J. P. Cryst. Growth Des. 2013, 13 (10), 4623−4629. (d) Kobayashi, Y.; Hernandez, O. J.; Sakaguchi, T.; Yajima, T.; Roisnel, T.; Tsujimoto, Y.; Morita, M.; Noda, Y.; Mogami, Y.; Kitada, A.; Ohkura, M.; Hosokawa, S.; Li, Z.; Hayashi, K.; Kusano, Y.; Kim, J. e.; Tsuji, N.; Fujiwara, A.; Matsushita, Y.; Yoshimura, K.; Takegoshi, K.; Inoue, M.; Takano, M.; Kageyama, H. Nat. Mater. 2012, 11 (6), 507−511. (e) Tezuka, K.; Tokuhara, Y.; Wakeshima, M.; Shan, Y. J.; Imoto, H.; Hinatsu, Y. Inorg. Chem. 2013,

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CONCLUSIONS Five single crystals of Ce(O,F)BiS2 grown from different starting materials were examined by single-crystal X-ray analysis. An increase in the F content supplied during growth produced single crystals with a nearly flat Bi−S(1) plane and enlarged Ce−(O,F) and Bi−S(2) bond lengths and shortened Ce−S(2) length. These crystals exhibit a superconductive transition at ∼3 K and magnetic ordering below ∼7 K. The Bi 6p and S 3p hybridized orbitals crossed the Fermi level, while the Ce 5d and 4f orbitals located near the Fermi level overlapped slightly with the S 3p and O/F orbitals. Therefore, the appearance of superconductivity can be related to the flat Bi−S(1) plane, and that of magnetic ordering could be E

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dx.doi.org/10.1021/cg5005165 | Cryst. Growth Des. XXXX, XXX, XXX−XXX