Crystal Structure and Magnetic and Magnetocaloric Properties of the Tb(Со_{1 – x}Fe_x)₂ and (Tb_{1 – z}Y_z)(Со_0.84Fe_0.16)₂ Compounds

Results of the study of the crystal structure and temperature and field dependences of magnetization, coercivity, and parameters of magnetocaloric effect of the polycrystalline TbCo₂-based compounds with Y and Fe, which substitute for the constituents in the 4f and 3d magnetic sublattices, are reported, respectively. The effect of the substitutions on the existence and value of crystal lattice rhombohedral distortions of the compositions studied at room temperature is shown. The substitution of Fe for 4–8 wt % Со was found to lead to the appearance of pronounced low-temperature maximum in the temperature dependence of the isothermal magnetic entropy change ∆S_m at temperatures 100–200 K below the Curie temperature. As a result, the increase in the refrigeration capacity coefficient q and working temperature range ∆T_FWHM is observed for the samples. At an iron content of ≥16 wt %, and also when Y substitutes for Tb, the decrease in q takes place because of the weak response of 4f-magnetic sublattice on the applied magnetic field near the low-temperature maximum. The obtained parameters of magnetocaloric effect are compared with those for the related compounds with the other rare-earth metals.