Thermally excited spin-disorder contribution to the resistivity of LaCoO₃

We have investigated the effect of the thermally induced spin-state transition on the electronic conduction mechanism in the perovskite LaCoO₃. The magnetotransport properties of this material are greatly influenced by this well studied spin-state transition. In fact, the excitation to a finite Co ion spin results in a thermal activation of spin disorder. This spin disorder is induced by thermal population of the nonzero spin states of the Co ions in zero magnetic field. The disorder is suppressed by a magnetic field leading to significant negative magnetoresistance effects, which are in effect thermally excited. We suggest that this material is an ideal testing ground for colossal magnetoresistive phenomena in a system where the complicating effects of lattice and magnetic phase transitions are not present.