Nanoanalysis of Co/Cu/NiFe thin films by tomographic atom probe

Abstract

Offering the possibility of improving data storage and magnetic sensoric, applications of giant magnetoresistance (GMR) in thin metallic films are of great interest. In order to study thermal reactions in such layered structures, atom probe tomography is used, which has been proven to perform a real three-dimensional analysis on the relevant length scale of several angstroms only. Co/Cu/Ni79Fe21 layered structures were deposited on tungsten substrate tips by ion beam sputtering and analyzed in the as-prepared state and after suitable heat treatments. After annealing at 250 °C for 30 min, Fe segregation at the Co/Cu interface inside the Co layer is clearly observed. This effect may be interpreted as an interface dusting potentially increasing the GMR. After annealing at 350 °C for 30 min, an additional Ni segregation inside Cu grain boundaries is observed. It is suggested that this segregation path forms the initial stage of pinhole formation and finally causes ferromagnetic bridges through the paramagnetic coupling layer.