Spatial manipulation of magnetic damping in ferromagnetic-antiferromagnetic films by ion irradiation

The static and dynamic magnetic properties of ferromagnetic-antiferromagnetic thin film stacks are manipulated in a controlled way by local ion treatment. Low fluence Ni-ion irradiation is used to adjust the magnetic damping parameter in ferromagnetic-antiferromagnetic-antiferromagnetic Ni81Fe19/IrMn/Ni81Fe19 sandwich structures. Moreover, the effective damping parameter is reduced spatially, from which a magnetic layer with bi-modal dynamic magnetic response results. The overall relaxation time of the mixed property film is found to be a direct superposition of the individual relaxation time contributions and thus determined by the ratio of phases with individual damping parameter. Multi-phase dynamic magnetic property films allow for an extra degree of freedom for the adjustment of magnetic properties in soft-magnetic thin films.