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

Offering the possibility of improving data storage and magnetic sensoric, a pplications of giant magnetoresistance (GMR) in thin metallic films are of great interest. In order to study thermal reactions in such layered structu res, atom probe tomography is used, which has been proven to perform a real three-dimensional analysis on the relevant length scale of several angstro ms only. Co/Cu/Ni79Fe21 layered structures were deposited on tungsten subst rate tips by ion beam sputtering and analyzed in the as-prepared state and after suitable heat treatments. After annealing at 250 degreesC for 30 min, Fe segregation at the Co/Cu interface inside the Co layer is clearly obser ved. This effect may be interpreted as an interface dusting potentially inc reasing the GMR. After annealing at 350 degreesC 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 fin ally causes ferromagnetic bridges through the paramagnetic coupling layer. (C) 2001 American Institute of Physics.