Thermodynamic features of magnetization and magnetocaloric effect near the magnetic ordering temperature of Gd

The magnetic field and temperature dependences of the adiabatic temperature change (Delta T) were measured in single-crystalline and polycrystalline gadolinium (Gd) near the Curie point (T(C)) by a direct method while continuously changing magnetic field (H) at different rates and the more conventional stepping of the magnetic field from 0 to 1.2 T. The Delta T(H) behavior has a tendency towards saturation at high magnetic fields, which is similar for both the polycrystal and the single crystal (in the latter case, the magnetic field vectors was parallel to the c-axis of the crystal). The Curie temperature of Gd was determined from Belov-Goryaga (Arrott) plots using isothermal magnetization data and a similar technique using adiabatic temperature change isotherms. In the latter case, T(C) was about 9 K higher than in the first case. Possible reasons for the observed difference are discussed. (C) 2007 Published by Elsevier B.V.