Abstract
Pure CaB6 single crystals are synthesized under high pressure (1 GPa) and temperature (1050°C). The temperature-dependence of electric resistivity and Hall coefficient from 2 to 300 K shows that the CaB6 single crystals are conductors with semi-metallic behavior and electron carriers. Band structure calculations indicate that the conduction and valence bands meet at the X point at the Fermi level, which is consistent with the experimentally determined conducting behavior of CaB6 single crystals. Calculations of state density suggest that the states at the Fermi level originate from the 2p orbital of the B atoms and the 3d orbital of the Ca atom. Magnetization measurements show the paramagnetic nature of the CaB6. The micro-hardness of CaB6 is 24.39 GPa, and the Raman spectra of CaB6 yield three sharp peaks at around 780.9, 1138.9, and 1282.1 cm−1 for T 2g, E g, and A 1g, respectively. The specific heat of the crystal is measured and found to be well described by the Debye and Einstein combined model. The fitting results show Debye and Einstein temperatures are 1119 and 199 K, respectively.
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References
Young D P, Hall D, Torelli M E, et al. High-temperature weak ferromagnetism in a low-density free-electron gas. Nature (London), 1999, 397: 412–414
Lin Z, Min G H, Yu H, et al. Sintering process and high temperature stability investigation for nano-scale CaB6 materials. Ceram Int, 2010, 36: 2253–2257
Cao M, Jiang J, Liu H, et al. The nature of Fe impurity phase in ferromagnetic CaB6. Physica B-Condens Matter, 2005, 364: 150–156
Norio O, Shinji N, Naoki O, et al. Raman scattering study of CaB6 and YbB6. J Solid State Chem, 2004, 177: 461–465
Cao M, Jiang J, Liu H, et al. Origin of ferromagnetism in polycrystalline Ca1+δ B6 (−0.05<δ<0.05) ceramics. Physica B-Condens Matter, 2005, 369: 39–43
Takao M, Shigeki O. Ferromagnetism in lanthanum doped CaB6: is it intrinsic? Solid State Commun, 2002, 123: 287–290
Vonlanthen P, Felder E, Wälti C, et al. Electronic transport and thermal properties of CaB6 and Eu1−x CaxB6. Physica B-Condensed Matter, 2000, 284–288: 1361–1362
Otani S, Mori T. Flux growth and magnetic properties of CaB6 crystals. J Phys Soc Jpn, 2002, 71: 1791–1792
Otani S, Mori T. Flux growth of CaB6 crystals. J Mater Sci Lett, 2003, 22: 1065–1066
Gavilano J L, Mushkolaj S, Rau D, et al. Anomalous NMR spin-lattice relaxation in SrB6 and Ca1−x LaxB6. Phys Rev B, 2001, 63: 140410(R)
Tromp H J, Gelderen P, Kelly P J, et al. CaB6: A new semiconducting material for spin electronics. Phys Rev Lett, 2001, 87: 016401
Denlinger J D, Clack J A, Allen J W, et al. Bulk band gaps in divalent hexaborides. Phys Rev Lett, 2002, 89: 157601
Gianno K, Sologubenko A V, Ott H R, et al. Low-temperature thermoelectric power of CaB6. J Phys Condens Matter, 2002, 14: 1035–1043
Massida S, Continenza A, de Pascale T M, et al. Electronic structure of divalent hexaborides. Z Phys B, 1997, 102: 83–89
Li Y, Yang J, Cui X, et al. Electrical properties of polycrystalline CaB6 under high pressure and low temperature. Phys Status Solidi (b), 2011, 248: 1162–1165
Morikawa T, Nishioka T, Sato N K. Ferromagnetism Induced by Ca Vacancy in CaB6. J Phys Soc Jpn, 2001, 70: 341–344
Hall D, Young D P, Fisk Z, et al. Fermi-surface measurements on the low-carrier density ferromagnet Ca1−x LaxB6 and SrB6. Phys Rev B, 2001, 64: 233105
Ott H R, Chernikov M, Felder E, et al. Structure and low temperature properties of SrB6. Z Phys B, 1997, 102: 337–345
Monnier R, Delley B. Point defects, ferromagnetism, and transport in calcium hexaboride. Phys Rev Lett, 2001, 87: 157204
Taniguchi K, Katsufuji T, Sakai F, et al. Charge dynamics and possibility of ferromagnetism in A −x LaxB6 (A=Ca and Sr). Phys Rev B, 2002, 66: 064407
Matsubayashi K, Maki M, Moriwaka T, et al. Extrinsic origin of high-temperature ferromagnetism in CaB6. J Phys Soc Jpn, 2003, 72: 2097–2012
Dorneles L S, Venkatesan M, Moliner M, et al. Magnetism in thin films of CaB6 and SrB6. Appl Phys Lett, 2010, 85: 6377–6379
Xin S, Han X, Liu S, et al. CaB6 single crystals grown under high pressure and high temperature. J Crystal Growth, 2010, 313: 47–50
Rhyee J S, Cho B K. The effect of boron purity on electric and magnetic properties of CaB6. J Appl Phys, 2004, 95: 6675–6677
Terashima T, Terakura C, Umeda Y, et al. Ferromagnetism vs paramagnetism and false quantum oscillations in lanthanum-doped CaB6. J Phys Soc Jpn, 2000, 69: 2423–2426
Meegoda C, Trenary M, Mori T, et al. Depth profile of iron in a CaB6 crystal. Phys Rev B, 2003, 67: 172410
Adams R M. Boron, Metallo-Boron Compounds and Boranes. New York: Welly, 1964. 233
Wigger G A, Felder E, Weyeneth S, et al. Kondo behavior of U in CaB6. Physica B-Condensed Matter, 2005, 359–361: 938–940
Vonlanthen P, Felder E, Degiorgi L, et al. Electronic transport and thermal and optical properties of Ca1-xLaxB6. Phys Rev B, 2000, 62: 10076–10082
Keppens V, Mandrus V D, Sales B C, et al. Localized vibrational modes in metallic solids. Nature, 1998, 395(6705): 876–878
Laird B B, Schober H R. Localized low-frequency vibrational modes in a simple model glass. Phys Rev Lett, 1991, 66(5): 636–639
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Xin, S., Liu, S., Zhao, Z. et al. Properties of CaB6 single crystals synthesized under high pressure and temperature. Sci. China Phys. Mech. Astron. 54, 1791 (2011). https://doi.org/10.1007/s11433-011-4453-3
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DOI: https://doi.org/10.1007/s11433-011-4453-3