Synthesis and properties of CaFe2As2 single crystals

We report the synthesis and basic physical properties of single crystals of CaFe2As2, a compound isostructural to BaFe2As2 which has been recently doped to produce superconductivity. CaFe2As2 crystallizes in the ThCr2Si2 structure with lattice parameters a = 3.887(4) Å and c = 11.758(23) Å. Magnetic susceptibility, resistivity, and heat capacity all show a first order phase transition at T0 = 171 K. The magnetic susceptibility is nearly isotropic from 2 to 350 K. The heat capacity data gives a Sommerfeld coefficient of 8.2 ± 0.3 mJ mol−1 K−2, and does not reveal any evidence for the presence of high frequency (>300 K) optical phonon modes. The Hall coefficient is negative below the transition, indicating dominant n-type carriers.

[1]  Liling Sun,et al.  Superconductivity at 55 K in Iron-Based F-Doped Layered Quaternary Compound Sm[O1-xFx] FeAs , 2008 .

[2]  Guizhen Wu,et al.  Superconductivity at 43 K in SmFeAsO1-xFx , 2008, Nature.

[3]  Huiqian Luo,et al.  Superconductivity at 36 K in gadolinium-arsenide oxides GdO1−xFxFeAs , 2008, 0804.0835.

[4]  Wei Lu,et al.  Superconductivity in the iron-based F-doped layered quaternary compound Nd[O1 − x Fx]FeAs , 2008, 0803.4234.

[5]  Gang Li,et al.  Superconductivity at 41 K and its competition with spin-density-wave instability in layered CeO1-xFxFeAs. , 2008, Physical review letters.

[6]  Hideo Hosono,et al.  Iron-based layered superconductor La[O(1-x)F(x)]FeAs (x = 0.05-0.12) with T(c) = 26 K. , 2008, Journal of the American Chemical Society.

[7]  M. Salamon,et al.  Hidden magnetism and quantum criticality in the heavy fermion superconductor CeRhIn5 , 2006, Nature.

[8]  C. Geibel,et al.  Observation of Two Distinct Superconducting Phases in CeCu2Si2 , 2003, Science.

[9]  J. L. Smith,et al.  Critical examination of heat capacity measurements made on a Quantum Design physical property measurement system , 2003 .

[10]  B. Delley,et al.  Strong electron-phonon coupling in superconducting MgB2: A specific heat study , 2001, cond-mat/0102522.

[11]  N. Mathur,et al.  Magnetically mediated superconductivity in heavy fermion compounds , 1998, Nature.

[12]  W. Müller-Warmuth,et al.  Magnetic properties of ternary lanthanoid transition metal arsenides studied by Mössbauer and susceptibility measurements , 1993 .

[13]  G. Nagorsen,et al.  Zur Struktur ternärer Übergangsmetallarsenide/On the Structure of Ternary Arsenides , 1980 .

[14]  R. Marchand,et al.  Ternary lanthanoid-transition metal pnictides with ThCr2Si2-type structure , 1978 .