THICKNESS AND MAGNETIC-FIELD DEPENDENCE OF THE FERROMAGNETISM OF ULTRATHIN GD FILMS IN GD W MULTILAYERS/

The magnetization of Gd/W multilayers with a constant W film thickness d(W) = 8 Angstrom prepared by electron-beam evaporation in UHV has be en studied by SQUID magnetometry as functions of the Gd layer thicknes s in the range of 8-85 Angstrom and of the external magnetic held. For the multilayer with 8 Angstrom Gd films, the Curie temperature T-c is reduced to 13 K. The thickness dependence of T-c follows the finite-s ize scaling except for the thinnest Gd films of 8 and 11 Angstrom. The magnetization induced by the external field at T-c is found to increa se with decreasing Gd film thickness. These observations are consisten t with a change from three- to quasi-two-dimensional Gd film behavior. (C) 1998 Elsevier Science B.V. All rights reserved.