Magnetic properties of thin epitaxial Gd films on Nb

We investigated the magnetic properties of Gd films by magnetization measurements with the transverse magnetooptic Kerr effect in the temperature range from 2 to 295 K and for magnetic field up to 0.3 T. The thicknessd _Gd of the Gd films was varied between 11 and 1000 Å. For thick films (d _Gd500 Å) the form of the hysteresis curves and especially the nonmonotonic temperature dependence of remanence and coercivity can be qualitatively reproduced with a simple model employing theT dependence of the easy-axis direction. TheT dependence of the saturation magnetizationM _s of the thick films (d _Gd>=150 Å) strongly resembles the behavior of bulk crystals, whereas for the thinnest filmsM _s approximately depends linearly onT up to the Curie temperatureT _C . The thickness dependence ofT _C follows approximately a power law with an exponent 1.6 close to the theoretical value.