Structure, transport properties and the magnetocaloric effect in Gd(Co 1− xNi x) 2 pseudobinary compounds

Abstract

A series of single phased Gd(Co 1− x Ni x ) 2 compounds were prepared by an arc-melting method. The crystal structure, transport properties and magnetocaloric effect have been investigated by X-ray powder diffraction, and by measuring the temperature dependences of electrical resistivity, magnetization and heat capacity. All the samples exhibit the same single Laves-phase MgCu 2-type structure, and lattice parameter a gradually decreases with increasing Ni content x . Only one paramagnetic–ferromagnetic (PM–FM) transition was found, and the Curie temperature T C decreases linearly with increasing x . The temperature dependences of electrical resitivity exhibit a metallic conductivity behaviour, and a clear change in slope near T C was found for all the present samples. The magnetic entropy change ( Δ S M ) and the adiabatic temperature change ( Δ T ad ) as a function of temperature in magnetic fields (1 T, 4 T and 7 T) were estimated from the results of isothermal magnetization at various temperatures and temperature dependence of heat capacity. The peak values of − Δ T ad and − Δ S M increase slightly with increasing x , and at a certain x they apparently increase with the increase of field. The Ni substitution effect on magnetic and transport properties, and the potential application of MCE for Gd(Co 1− x Ni x ) 2 compounds are also discussed.