Thermodynamics of the ferromagnetic phase transition in nearly half metallic CoS2 at high pressures

The volume change and heat capacity at the ferromagnetic phase transition in CoS2 were measured at high pressures using X-rays generated by the Argonne synchrotron light source and by ac-calorimetry, respectively. The transition entropy, calculated on the basis of these experimental data, drops along the transition line due to quantum degradation, as required by Nernstʹs law. The volume change increases strongly along the transition line, which is explained by specifics of the compressibility difference of coexisting phases that results from nearly half metallic nature of the ferromagnetic phase of CoS2.