Heavy Fermion Behavior, Crystalline Electric Field Effects, and Weak Ferromagnetism in SmOs_{4}Sb_{12}

TL;DR

This study investigates the heavy fermion behavior, crystalline electric field effects, and weak ferromagnetism in the filled skutterudite compound SmOs₄Sb₁₂, revealing large electronic specific heat, CEF splitting, and a possible weak ferromagnetic transition.

Contribution

It provides the first detailed characterization of SmOs₄Sb₁₂, highlighting its heavy fermion nature, CEF splitting, and magnetic properties, which were not previously reported.

Findings

Large electronic specific heat coefficient (~880 mJ/mol K^2) indicating heavy fermion behavior.

Crystalline electric field splitting of ~37 K between ground and excited states.

Possible weak ferromagnetic transition at ~2.6 K.

Abstract

The filled skutterudite compound SmOs_{4}Sb_{12} was prepared in single crystal form and characterized. The SmOs_{4}Sb_{12} crystals have the LaFe_{4}P_{12}-type structure with lattice parameter a = 9.3085 Angstroms. Specific heat measurements indicate a large electronic specific heat coefficient of ~880 mJ/mol K^{2}, from which an enhanced effective mass m^{*} ~ 170 m_{e} is estimated. The specific heat data also suggest crystalline electric field (CEF) splitting of the Sm^{3+} J = 5/2 multiplet into a Gamma_{7} doublet ground state and a Gamma_{8} quartet excited state separated by 37 K. Electrical resistivity rho(T) measurements reveal a decrease in rho(T) below ~50 K that is consistent with CEF splitting of ~33 K between a Gamma_(7) doublet ground state and Gamma_{8} quartet excited state. Specific heat and magnetic susceptibility measurements display a possible weak ferromagnetic transition at ~2.6 K, which could be an intrinsic property of SmOs_4Sb_{12} or possibly due to an unknown impurity phase.