Large magnetic entropy change and relative cooling power in the rare earth intermetallic HoCo0.25Ni1.75 compound

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 (T-c). The magnetization vs field (M-mu H-0) isotherm at 2 K shows negligible hysteresis. The isothermal magnetic entropy change (Delta S-m) is calculated from the measured M-mu H-0 data near T-c. The maximum value of Delta S-m, Delta S-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 Delta S-m(max) of -9.4 J/kg-K even for a low field change of 2 T. Universal master curve is constructed by rescaling Delta S-m vs T curves for various fields to confirm the second order nature of the magnetic transition at T-c. Large Delta S-m(max) 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. (C) 2015 Elsevier B.V. All rights reserved.