Large magnetic entropy change and relative cooling power in the rare earth intermetallic HoCo<inf>0.25</inf>Ni<inf>1.75</inf> compound

Abstract Magnetic and magnetocaloric properties of cubic Laves phase rare earth intermetallic HoCo0.25Ni1.75 compound have been investigated. Magnetization measurements show that HoCo0.25Ni1.75 orders ferromagnetically at 22 K (TC). The magnetization vs field (M-μ0H) isotherm at 2 K shows negligible hysteresis. The isothermal magnetic entropy change (ΔSm) is calculated from the measured M-μ0H data near TC. The maximum value of ΔSm, ΔSmmax, is about -18.9 J/kg-K at TC for a field change of 5 T with a refrigerant capacity of 572 J/kg. The material exhibits large ΔSmmax of -9.4 J/kg-K even for a low field change of 2 T. Universal master curve is constructed by rescaling ΔSm vs T curves for various fields to confirm the second order nature of the magnetic transition at TC. Large ΔSmmax value, wide temperature span of cooling and high relative cooling power make HoCo0.25Ni1.75 a potential magnetic refrigerant for low temperature applications such as hydrogen liquefaction.