Magnetic properties and magnetocaloric effect in Gd films and microwires

Abstract

An analysis of the temperature and field dependences of the magnetization of Gd films and microwires was carried out, as well as an isothermal measurement of the magnetic part of the entropy at the Curie temperature. The magnetocaloric effect (MCE), measured as an isothermal increase in the magnetic part of the entropy, in microwires shows two peaks on the temperature dependence of the magnetic part of the entropy, in contrast to one peak in films. In films and microwires, the entropy maximum at 286-293 K, which corresponds to the Curie temperature, depends on the magnetic field, shifting in the same way in films and microwires with an increase in the field at the orientation of the MgO (111) substrate, which provides the maximum mechanical stresses in Gd. In microwires, the second maximum does not change the temperature of 320 K as the field increases to 9 T, but its amplitude increases linearly with the field. This maximum can be caused by a spin-reorientation transition. Keywords: microwires, thin films, magnetic entropy, magnetic anisotropy, spin-reorientation transition, Curie temperature.