MAGNETIZATION OF THIN GD FILMS ON W(110) NEAR THE CURIE-TEMPERATURE

In situ temperature dependent magneto-optic Kerr effect measurements i n ultrahigh vacuum are presented for 80 and 300 angstrom thick Gd(0001 ) films. Films were deposited at 300 K and stepwise annealed to 820 K. It was found that the remanent magnetization M(r)(T) depends on the a nnealing temperature. The as-deposited films have a reduced Curie temp erature T(c), e.g., T(c)(80 angstrom)=273 K, which gradually shifts up to the bulk T(c) of Gd upon annealing. The changes in M(r)(T) are cor related with a sharpening of the Gd low energy electron diffraction pa ttern. The best magnetic homogeneity and structural coherence is found for films annealed to 620 K. At higher temperatures the films break u p into large three-dimensional islands with nearly uncovered W areas i n between (W Auger is observed). The magnetic behavior was simulated w ith a model which assumes a Gaussian distribution of T(c) values. From these simulations and the known bulk pressure dependence of T(c) we e stimate the mean strain and the strain distribution within the films.