Magnetic moment, thermal and electrical transport in the inverse Mott systems BaCo0.9Ni0.1S2−y and CuIr2S4

Abstract

The antiferromagnetic BaCo0.9Ni0.1S2−y and the paramagnetic CuIr2S4 Mott systems show an inverse conductivity behavior, i.e., the metallic phase occurs at low or high temperatures, respectively, which also suggests inverse behavior in other transport properties. In this contribution we present magnetization data, conductivity, thermal conductivity, and Seebeck effect in the temperature range 4.2 K<T<350 K and in particular through the metal-insulator transition at TMI. We recover the anomalies in χ(T),σ(T), which are discussed using Jahn-Teller and anti-Jahn-Teller models; also, we compare the anomalies in σ(T), S(T), and of the heat conductivity κ(T) at TMI. In particular, for BaCo0.9Ni0.1S1.95, we find a step in κ of almost one order of magnitude (times 6) and a large pressure shift, ⩽−24 K/kbar, which makes this material a potential pressure activated heat switch, while CuIr2S4 shows a small step of κ (times 1.2) and a pressure shift of +2.8 K/kbar.