Relation of domain properties to structural changes in perpendicularly magnetized ultrathin films

The influence of interface mixing upon the magnetic domain properties in pe rpendicularly magnetized ultrathin films has been studied using Fe/2 ML Ni/ W(110) samples. Annealing of films with an Fe thickness of 1-1.5 ML produce s interface mixing that can be quantified using Auger electron spectroscopy , and related to the changes in domain properties (such as the activation e nergy for domain wall pinning, the domain correlation length. and domain co ncentration) as measured by the low frequency sc magnetic susceptibility. A nalysis of the susceptibility. as well as model calculations of the magneti c anisotropy, suggest that pinning is caused bq the perturbation of the dom ain wall energy by monolayer steps in thickness. Initially, annealing smoot hs the him, thus increasing the domain correlation length and activation en ergy. Further annealing causes mixing at the Fe/Ni interface, which reduces the anisotropy, thus reducing the activation energy and increasing the dom ain concentration. Annealing above 550 K breaks up the film and there is no magnetic response in the measurable temperature range.