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In this work we report the results of experimental investigation of the magnetocaloric effect in Gd100-xZrx(x= 0, 1, 2, 3) cold rolled ribbons. As it is shown the magnetocaloric effect exist within the large temperature interval 279-295 K and comparable with magnetocaloric effect observed on pure Gd. As it shown cold rolling is one of promising techniques for producing thin forms of magnetocaloric materials for heat exchangers of magnetic cooling devices.

The direct measurements of the magnetocaloric effect (MCE) and the magnetization for R2Fe17 (R = Y, Tb, Dy) compounds are reported. The maximal values of the MCE for different R2Fe17 compounds are almost the same at the Curie temperature and are equal to 0.8 – 0.85 K at ΛH = 13.5 kOe. The field dependencies of the magnetization and MCE and the dependence of MCE via magnetization deviates from the classical regularities and describes by the thermodynamic theory attracting the higher terms. Obviously the occurrence of the mixed exchange interactions in these compounds leads to the requirement of consideration both thermal and local fluctuations of the exchange integrals near the magnetic transition temperature.

In this work we report the results of investigation of the magnetocaloric effect in Gd100-xYx (x= 0, 5, 10, 15) cold rolled ribbons. It is shown that the magnetocaloric effect exists within a wide temperature interval 258-295 K and it is comparable with the magnetocaloric effect observed in bulk samples of pure gadolinium. The value of the magnetocaloric effect in the rolled samples is reduced in comparison with the bulk samples and strongly depends on a degree of plastic deformation. High temperature heat treatment can restore a value of the magnetocaloric effect in the cold rolled ribbons up to initial ones. Thus, cold rolling is proposed to be a promising technique for producing thin forms of magnetocaloric materials for heat exchangers of magnetic cooling devices.

A model for Brayton cooling cycles used in magnetic refrigeration near room temperature was developed. This model was used to calculate a theoretical limit of temperature span and cooling power. The cooling power was calculated for single and double Brayton cooling cycles with Gd as the working body. The obtained results clearly demonstrate the functional ranges of Bryton-cycle refrigerators.

Direct measurements of the magnetocaloric effect (MCE) in RCo5 single crystals in the region of spin-reorientation transitions (SRT) were carried out. It was shown that the values of MCE in the region of SRTs are comparable to the values of MCE in the vicinity of the Curie temperature. The anisotropy constants of the compounds were measured by the torque method. The anisotropic MCE calculation on the basis of anisotropy constants showed a good accordance with the experimental data.

Characteristics of the temperature transformation of magnetic domain structure (DS) during different spin reorientation transitions (SRT) are analyzed on the basis of DS investigations of R2Fe14B, RFe11Ti, RCo5, R2Fe17 single crystals (R = Nd, Gd, Tb, Dy, Ho, Er) in the temperature interval of 4.2 - 400 K.