Enhanced magnetocaloric effect in undercooled rare earth intermetallic compounds RNi (R = Gd, Ho and Er)

Abstract

Equiatomic RNi (where R = Gd, Ho and Er) compounds have been prepared by undercooling. Magnetization data confirm ferromagnetic ordering of the samples at 69 K, 35 K and 10 K (TC) respectively. Magnetocaloric effect (MCE) has been estimated in terms of isothermal magnetic entropy change (ΔSm) near TC. The maximum ΔSm value (ΔSmmax) for 50 kOe field change is about −18 Jkg-1K−1, −20 Jkg-1K−1 and −30 Jkg-1K−1 respectively near TC for the undercooled RNi (R = Gd, Ho and Er) compounds. The ΔSmmax value is more than that obtained for the same compounds prepared by arc-melting and melt-spinning techniques. The observed enhancement in MCE of the undercooled samples could be due to the improved purity that results in faster change of magnetization around the magnetic transition. Thus undercooling rare earth intermetallics and alloys seems to be an attractive, alternative method to synthesize magnetocaloric materials.