The influence of spontaneous and field induced spin reorientation transitions on the magnetocaloric properties in rare earth intermetallic compounds: Application to TbZn

摘要

We report a theoretical investigation on the magnetocaloric properties of the cubic CsCl-type TbZn compound. Two successive peaks in the magnetocaloric quantities are observed and attributed to different types of phase transitions. For the magnetic field applied in the (110) direction, the first peak is ascribed to a spontaneous first-order spin reorientation transition (SRT) at T_1 = 63 K, and the second one to the ferroparamagnetic phase transition. The application of an external magnetic field of 2 T along this direction leads to a tablelike behavior in the magnetocaloric quantities (ΔS_T and ΔT_S) as a consequence of two successive second-order SRTs at T_(SR1) = 71 K and at T_(ST2)=160 K. Applying a magnetic field of 5 T suppress the flat behavior but a high refrigeration capacity of 352 J/kg is predicted in a wide temperature range from 62 to 258 K. When the magnetic field is applied along the (100) direction an inverse magnetocaloric effect is observed in the temperature range below T_1. The system -was studied throughout a Hamiltonian that takes into account the Zeeman, exchange, and crystal field interactions.