Effect of Substitution of Co by Ni on the Magnetic Properties and Magnetocaloric Effect of Ho((Co1 – yNiy)0.84Fe0.16)2 Compounds

The structure and the magnetic and magnetocaloric properties of Ho((Co1 – yNiy)0.84Fe0.16)2 compounds are investigated. The substitution of Co by Ni leads to weakening of the energy of the 4f–3d sublattice exchange interaction and to the appearance of a pronounced low-temperature maximum in the temperature dependence of the change in the magnetic entropy (∆Sm). As a result, the ∆Sm values increase by a factor of up to 2. The calculated values of the heat capacity (q) are comparable to or exceed the q values for metallic Gd.