Large magnetic entropy change and relative cooling power in the rare earth intermetallic HoCo_0.25Ni_1.75 compound

Magnetic and magnetocaloric properties of cubic Laves phase rare earth intermetallic HoCo_0.25Ni_1.75 compound have been investigated. Magnetization measurements show that HoCo_0.25Ni_1.75 orders ferromagnetically at 22 K (T_C). The magnetization vs field (M–μ₀H) isotherm at 2 K shows negligible hysteresis. The isothermal magnetic entropy change (ΔS_m) is calculated from the measured M–µ₀H data near T_C. The maximum value of ΔS_m, ΔS_m^max, is about −18.9 J/kg-K at T_C for a field change of 5 T with a refrigerant capacity of 572 J/kg. The material exhibits large ΔS_m^max of −9.4 J/kg-K even for a low field change of 2 T. Universal master curve is constructed by rescaling ΔS_m vs T curves for various fields to confirm the second order nature of the magnetic transition at T_C. Large ΔS_m^max value, wide temperature span of cooling and high relative cooling power make HoCo_0.25Ni_1.75 a potential magnetic refrigerant for low temperature applications such as hydrogen liquefaction. - Highlights: • A large magnetocaloric effect is observed in Laves phase HoCo_0.25Ni_1.75 compound. • The isothermal magnetic entropy change ΔS_m vs T of HoCo_0.25Ni_1.75 is broad near T_C. • The magnetization vs field isotherms have negligible hysteresis. • A large relative cooling power is realized in HoCo_0.25Ni_1.75. • Universal master curve is constructed by rescaling ΔS_m vs T data