Les propriétés magnétocaloriques et la conductivité thermique du Gd.

Thermodynamic data of pure Gd (99.95), of technical available Gd (99.5) and of plastically deformed Gd are presented. For this purpose the temperature dependence of the specific heat and magnetic measurements M(H,T) have been performed. Additional measurements of the thermal conductivity (using a flash method) are presented. Studies of the magnetostriction just above TC indicate a strong polarization effect. For dynamic applications in a closed magnetic circuit, hysteresis measurements as a function of frequency were performed. The frequency dependence of the coercivity is analysed considering eddy current effects. The frequency dependence of the losses shows also the influence of classical eddy currents as well as excess losses. Approaching TC the ratio of the different eddy current contributions changes significantly.