Temperature and field dependent electronic structure and magnetic properties of LaCoO3 and GdCoO3

The transformation of the band structure of LaCoO₃ in the applied magnetic field has been theoretically studied. If the field is below its critical value B_C≈65 T, the dielectric band gap decreases with the field, thus giving rise to negative magnetoresistance that is highest at T≈300÷500 K. The critical field is related to the crossover between the low- and high-spin terms of Co³⁺ ions. The spin crossover results in an insulator–metal transition induced by an increase in the magnetic field. Similar calculations have been done for GdCoO₃ which is characterized by large spin gap∼2000 K.