Direct imaging of spin relaxation in stepped alpha-Fe2O3/Ni81Fe19 bilayers using X-Ray PhotoEmission Electron Microscopy

The magnetic domain structure of stepped ferromagnetic Ni81Fe19 films, exchange coupled to antiferromagnetic alpha-Fe2O3, has been studied using PhotoEmission Electron Microscopy combined with X-Ray Magnetic Circular Dichroism. Annealing the alpha-Fe2O3/Ni81Fe19 bilayers in a magnetic eld, applied parallel or perpendicular to the step edges, results in a signifcant increase in the domain size compared to the as-grown bilayer. Subsequent zero-eld annealing induces spin-relaxation along the crystallographic axes of the alpha-Fe2O3. The spin-relaxation process is found to depend on the magnetic field direction during annealing with the domain structure determined by a competition between the step-induced uniaxial anisotropy and the exchange anisotropy.