Magnetism and electron redistribution effects at Ni/Co interfaces

The electronic structure at the Ni/Co interface has been characterized using differences in L-2,L-3 x-ray-absorption spectra (XAS) recorded before and after deposition of Ni overlayers on Co films. Strong changes in the Co and Ni absorption spectra suggest a high degree of d-charge redistribution between the Co and Ni d states for submonolayer coverages of Ni. X-ray magnetic circular dichroism shows that the change in the d-state occupancies results in an increased Co spin moment and a reduced Ni spin moment. The effects are interpretted in terms of a modified exchange splitting of the Ni and Co d bands determined using line-shape analysis of Co XAS. The results are compared with the predictions of first-principles band-structure calculations invoking the local spin-density approximation.