Gap suppression and development of antiferromagnetic order in CeRh_1-xPd_xSb: heat-capacity studies

Abstract

CeRhSb is a mixed-valent compound in which a gap opens up in the electronic density of states below a temperature of about 10 K. Earlier studies on Pd substitution at the Rh site in this compound showed that the gap is suppressed for around 10% Pd and an antiferromagnetic ground state emerges with higher Pd substitution. Here, we report heat-capacity results on some of these samples, namely, CeRh_0.8Pd_0.2Sb and CeRh_0.7Pd_0.3Sb. We observe a sharp rise in C_4f/T of CeRh_0.7Pd_0.3Sb starting at around 5 K with a peak at about 2.5 K, which confirms the antiferromagnetic ordering in this compound. An entropy change of 2.5 J/mol K is obtained for the ordering. Above the Neel temperature, the value of the electronic specific heat coefficient γ is found to be about 40mJ/mol K². In CeRh_0.8Pd_0.2Sb, C_4f/T is found to rise below 10 K down to the lowest temperature of measurement, namely, 1.5 K with a γ value of about 40mJ/mol K². The rise may be due to non-Fermi-liquid behavior or could be due to impending magnetic order in the compound below 1.5 K.