Magnetism and superconductivity in the Heusler alloy Pd2YbPb


Oner Y.

JOURNAL OF APPLIED PHYSICS, cilt.111, 2012 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 111 Konu: 7
  • Basım Tarihi: 2012
  • Doi Numarası: 10.1063/1.3671780
  • Dergi Adı: JOURNAL OF APPLIED PHYSICS

Özet

We report the temperature dependence (1.8-300 K) of the heat capacity (C-p) and electrical resistivity (rho) for the Heusler alloy Pd2YbPb and its isomorphous nonmagnetic counterpart, Pd2YPb. Both compounds appear to be the same MnCu2Al structure with space group Fm (3) over barm. From the resistivity data, the superconducting transition for Pd2YbPb and Pd2YPb are observed at T = 2.85 K and T = 4.75 K, respectively. At low temperatures, the Cp/T versus T data exhibits a small jump at around 4 K for Pd2YPb, while, for Pd2YbPb, this superconducting transition is hidden by an upturn feature observed below T = 3 K, presumably due to nuclear spin polarization. From low temperature analysis of the Cp/T data, the electronic contribution to C-p and Debye temperature were determined to be gamma = 4.5 mJ/mole-K and Theta(D) = 140 K for Pd2YbPb and gamma = 1.6 mJ/mole-K and Theta(D) = 173 K for Pd2YPb. The magnetic contribution of the Yb+3 ions to the heat capacity and resistivity were calculated by subtracting the Pd2YPb data from that for Pd2YbPb. The scheme of the energy levels created by the crystal electric field (CEF) splitting for cubic symmetry was determined from the Schottky contribution to C-p. In addition, the effect of CEF on the resistivity has been investigated. Both analyses lead us to suggest that the ground state of Yb ions is a quartet Gamma(8). The first excited level between the ground state Gamma(8) and a Gamma(7) doublet, Delta(1) = 125 K, and the second energy splitting between Gamma(8) and Gamma(6), Delta(2) = 268 K, were deduced from the heat capacity data, while values of Delta(1) = 155 K and Delta(2) = 355 K were obtained from resistivity data. Furthermore, at higher temperatures, we observed that C-p for Pd2YbPb exceeds the Dulong-Petit limit, leading us to include a small anharmonic correction in the fitting analysis. (C) 2012 American Institute of Physics. [doi:10.1063/1.3671780]