Magnetization of thin Gd films on W(110) near the Curie temperature

Abstract

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