Structure, transport properties and the magnetocaloric effect in Gd(Co1−xNix)2 pseudobinary compounds

A series of single phased Gd(Co1−xNix)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 MgCu2-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 TC decreases linearly with increasing x. The temperature dependences of electrical resitivity exhibit a metallic conductivity behaviour, and a clear change in slope near TC was found for all the present samples. The magnetic entropy change (ΔSM) and the adiabatic temperature change (ΔTad) 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 −ΔTad and −ΔSM 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(Co1−xNix)2 compounds are also discussed.