Thermodynamic model of the magnetocaloric effect near the first-order magnetic phase transitions

Magnetocaloric effect (MCE) arising in the materials with the first-order magnetic phase transitions (such as heavy rare earth metals, FeRh and GdSiGe alloys, lanthanides) has been considered in the framework of thermodynamic approach. The exchange, magnetoelastic, anisotropic and magnetic energy contributions to the MCE and their temperature dependences were calculated in the vicinity of the first-order transition. It was shown that the model adequately describes the MCE and gives the values of the adiabatic temperature change and isothermal magnetic entropy change, which are in accord with direct experimental measurements. Possible mechanisms of the MCE near the first-order transitions are discussed.