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

Abstract

The crystal structures of Ce(O,F)BiS 2 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.

Ce 4f electronic states of CeO1−xFxBiS2 studied by sof

“…The nominal composition of F was set to be x = 0.7. Details on the sample preparation and characterization are given elsewhere [18,19,21,24].…”

“…Furthermore, it is concluded that the superconducting and the magnetically ordered states coexist for higher x at low temperatures [12][13][14][15]. These findings have caused particular interest in this compound and stimulated further investigations of it [16][17][18][19][20][21][22][23]. The phase diagrams, obtained by systematic investigation for nominal F-concentration (x) dependence (x = 0.0-1.0) of both the magnetic ordering and the superconducting properties of the as-grown polycrystalline samples, show that ferromagnetic-like ordering occurs at slightly higher temperature than the superconducting transition for x > 0.4 [21].…”

“…In contrast, for single-crystal samples, the same trend with the as-grown samples (T c < T m ) is observed. For example, the magnetic ordering temperature T m is 5.6 K and the superconducting transition temperature T c (estimated by Meissner effect) is 3.0 K for x = 0.7 [19,24]. The Ce L 3 edge x-ray absorption spectroscopy (XAS) measurements for polycrystalline samples show a crossover from mixed valence states to the localized 4f states under F doping [16].…”

Evolution of superconductivity and magnetism in BiS2-based layered compounds

“…In addition, two types of magnetic ordering and superconductivity are observed in single crystals of CeO 1−x FxBiS 2 [70]. Figure 13 shows the temperature dependence of the magnetization for single crystals of CeO 1−x FxBiS 2 .…”

Electronic structure predictions in Bi-O-S systems

“…The other subfamily, which branched out of research on La(O,F)BiS 2 , has been studied extensively. Magnetic order and charge density wave order have been found, both theoretically and experimentally [5][6][7][8][9][10][11][12][13][14][15].…”