Transport and Magnetic Properties of a Low-Density Carrier System SmBiPt

Abstract

We present the results of electrical resistivity ρ, Hall coefficient R_H, thermoelectric power S, specific heat C and magnetic susceptibility χ on SmBiPt with the MgAgAs-type structure. ρ(T) and S(T) exhibit a broad maximum of 1.7 mΩcm at 80 K and 60 μV/K at 126 K, respectively. These facts and the change of R_H from negative to positive on cooling through 200 K indicate the semimetallic nature of SmBiPt. At around 7 K, ρ(T) and S(T) show a shallow dip and a small peak, respectively. The antiferromagnetic order at T_N= 2.2 K is manifested as a sudden drop in ρ and a peak in both C and χ. The magnetic entropy at T_N is 0.6Rln4 and reaches a plateau of Rln4 at 18 K, indicating the Γ₈ quartet ground state of Sm³⁺ in this cubic compound. The results of χ(T) and magnetization curve can be explained by considering the mixing of higher multiplet levels of J=7/2 and 9/2 into the ground multiplet of J=5/2.