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.