Magnetic anisotropy in MBE-grown epitaxial gadolinium ultra-thin films

The structure and magnetic properties of gadolinium thin films in two syste ms: W/Gd/W and Y/Gd/Y were studied. Gd films were grown epitaxially on tung sten and yttrium buffer layers in UHV MBE facility using e-guns as the evap oration source. Monocrystalline sapphire substrates with (1 1 (2) over bar 0) crystallographic orientation were used. Critical thickness of d(c) = 3 A ngstrom for gadolinium deposited epitaxially on tungsten was determined - i n the first monolayer lattice expansion of 3.5% was observed comparing to t he bulk gadolinium. Significant decrease of Curie temperature with decreasi ng of Gd thickness was found. In Y/Gd/Y system for all studied range of Gd thickness (160 > X > 9 Angstrom) inplane anisotropy was observed. On the co ntrary, in W/Gd/W system for Gd thickness below 40 Angstrom the transition from in-plane to perpendicular anisotropy took place. (C) 2000 Elsevier Sci ence S.A. All rights reserved.