Anomalies of the electronic structure and physical properties of rare-earth cobaltites near spin crossover

The features of the characteristics of LnCoO₃ cobaltites, where Ln is a rare-earth element, are discussed. Both experiment and theory demonstrate that their essentials are related to the low-spin ground state of cobalt ions. The thermally induced occupation of the excited high-spin state gives rise to peaks in the magnetic susceptibility, specific heat, and thermal expansion, as well as to a smooth insulator–metal transition. The analysis is based both on the data from the current literature concerning LaCoO₃ and in many aspects on our own studies of GdCoO₃ and La_1?x Gd _x CoO₃ solid solutions.