Thermally and field-driven spin-state transitions in (Pr1−yYy)0.7Ca0.3CoO3

The first-order character of the transition from the low-to-intermediate spin state in the system (Pr1−yYy)0.7Ca0.3CoO3 (y = 0.075–0.15) has been verified by magnetization measurements. For y = 0.075, the transition manifests itself in χ(T) steps at temperatures depending on external fields. In this case, isothermal measurements show a field-driven transition exhibiting a field hysteresis. The entropy contribution is evaluated and discussed. Qualitative analysis based on a two-level model suggests that the observed influence of the magnetic field can be explained only by assuming the presence of exchange interactions.