[Zurück]

Y. Kawamura, S. Deminami, K. Takeda, T. Kuzuya, L. Salamakha, H. Michor, E. Bauer, J. Gouchi, Y. Uwatoko, T. Kawae, C. Sekine:
"Crystallographic and superconducting properties of filled skutterudite SrOs₄P₁₂";
Physical Review B, 103 (2021), 085139; S. 1 - 9.

The crystallographic and physical properties of the recently discovered filled skutterudite superconductor SrOs₄P₁₂, synthesized by a high-pressure and -temperature technique, are studied by measuring electrical resistivity, specific heat, and magnetization, and by performing electronic band calculations. X-ray powder diffraction with Rietveld refinement indicates that the lattice parameter of SrOs₄P₁₂ is 8.093(2) Å and that fractional coordinates of the P site are [0, 0.3607(9), 0.1450(9)], which is also confirmed by calculations based on density functional theory. The electrical resistivity indicates a metallic nature of SrOs₄P₁₂, which is consistent with the density of states at Fermi energy with 7.5 (states/eV)/f.u. deduced from the electronic band calculations. The Sommerfeld coefficient γ and Einstein temperature Θ_E of SrOs₄P₁₂ are deduced as γ∼26mJ/molK² and Θ_E∼150 K, respectively. A larger isotropic atomic displacement parameter U_eq of Sr compared to other atomic species as obtained from a Rietveld analysis and a specific heat anomaly around 30 K refers to anharmonic lattice vibrations of Sr in SrOs₄P₁₂. SrOs₄P₁₂ exhibits two superconducting transitions at T_c1=1.6 K and T_c2=1.0 K. Specific-heat data indicate that the observed superconductivity is of bulk nature with approximate volume fractions of 27% and 38% for superconductivity at T_c1 and T_c2, respectively. The electrical resistivity under field and pressure as well as the specific heat under field indicate that T_c1 is sensitive to the magnetic field and T_c2 is sensitive to pressure. The results show that T_c2 is an s-wave weakly coupled superconductor with an electron-phonon mass enhancement λ_ep∼0.47.

alkaline earth metals, superconductivity

http://dx.doi.org/10.1103/PhysRevB.103.085139