The magnetocaloric effect in Gd/sub 7/Pd/sub 3/ and Gd/sub 7/Pd/sub 3-x/Ni/sub x/ compounds

Summary form only given. Magnetic refrigeration, based on materials showing high magnetocaloric properties, is at present a valuable alternative to gas compression technology, because of the high thermodynamic efficiency due to the reversibility of the magnetocaloric effect and the high energy densities exhibited in compact devices, coupled with the absence of ozone depleting CFC´s as liquid refrigerants. As a part of a current research concerning the physical characterization of Rare Earth intermetallic compounds for magnetic refrigeration devices, the magnetocaloric properties of the Gd/sub 7/Pd/sub 3/ phase, which crystallises in the Th/sub 7/Fe/sub 3/ hexagonal structure type and shows a ferromagnetic transition below 318 K, are presented. Heat capacity measurements have been performed in the 5-360 K temperature range and for applied magnetic fields up to 5T. Basing on the heat capacity data the isothermal entropy change S/sub M/ and the adiabatic temperature raise T/sub ad/ have been calculated (S/sub M/ = 6.5 J/Kkg and T/sub ad/ = 8.5K at 5T and 320K). From the S/sub M/ vs T plot the refrigerant capacity Q /sup Tf/ /sub Ti/ S/sub M/ (T)dT has been determined. The Q values obtained for the Gd/sub 7/Pd/sub 3/ phase together with some reference data are reported. Furthermore, in this work the influence of partial Pd substitution with Ni on the transition temperature and on the magnetocaloric properties is also examined.