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 thickness d(Gd) of the Gd films was varied between 11 and 1000 angstrom. For thick films (d(Gd) greater-than-or-equal-to 500 angstrom) 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 the T dependence of the easy-axis direction. The T dependence of the saturation magnetization M(S) of the thick films (d(GD) greater-than-or-equal-to 150 angstrom) strongly resembles the behavior of bulk crystals, whereas for the thinnest films M(S) approximately depends linearly on T up to the Curie temperature T(C). The thickness dependence of T(C) follows approximately a power law with an exponent lambda almost-equal-to 1.6 close to the theoretical value.