Magnetic and magnetocaloric properties of rare earth intermetallic compounds HoCo_2−xNi_x (x=0.75 and 1.25)

Magnetic and magnetocaloric properties of polycrystalline rare earth intermetallic compounds HoCo_2−xNi_x (x=0.75 and 1.25) have been investigated. Both HoCo_1.25Ni_0.75 and HoCo_0.75Ni_1.25 compounds crystallize in MgCu₂ type, cubic Laves phase structure (space group Fd3^¯m, no. 227) and order ferromagnetically at ∼40 K and ∼36 K (T_C) respectively. Field dependent magnetization at 5 K shows soft ferromagnetic behavior. The saturation magnetization value is about 8.5 μ_B/f.u. for both compounds. Magnetocaloric effect in HoCo_2-xNi_x (x=0.75 and 1.25) compounds has been evaluated in terms of isothermal magnetic entropy change (ΔS_m) that peaks around T_C with maximum values of about −16.7 J/kg K and −15.2 J/kg K, respectively, for a field change of 70 kOe. Substitution of Ni at the Co-site of HoCo₂ broadens the magnetic transition and enhances relative cooling power which makes these materials suitable for low temperature magnetic refrigeration applications