Magnetic and magnetocaloric properties of rare earth intermetallic compounds HoCo2−xNix (x=0.75 and 1.25)

Magnetic and magnetocaloric properties of polycrystalline rare earth intermetallic compounds HoCo2−xNix (x=0.75 and 1.25) have been investigated. Both HoCo1.25Ni0.75 and HoCo0.75Ni1.25 compounds crystallize in MgCu2 type, cubic Laves phase structure (space group Fd3¯m, no. 227) and order ferromagnetically at ~40 K and ~36 K (TC) respectively. Field dependent magnetization at 5 K shows soft ferromagnetic behavior. The saturation magnetization value is about 8.5 μB/f.u. for both compounds. Magnetocaloric effect in HoCo2-xNix (x=0.75 and 1.25) compounds has been evaluated in terms of isothermal magnetic entropy change (ΔSm) that peaks around TC 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.