Magnetic coupling in spin-valves from magnetic circular dichroism

摘要

The authors have applied magnetic x-ray circular dichroism (MXCD) to extract elemental magnetic moments for real, thin-film spin valve devices and demonstrated the correlation between MXCD and R-H measurements on those devices. The spin valves consisted of NiFe/Co/Cu/Co/NiFe sandwiches with variable Cu spacer-layer thickness, grown on a thick NiO film, as described previously. One permalloy layer is therefore magnetically pinned to the substrate which it contacts. Spin-polarized, X-ray absorption spectra were collected using beamline 8-2 at the Stanford Synchrotron Radiation Laboratory. The Poynting vector of the incident beam was aligned at grazing incidence to the films, either parallel or antiparallel to their remanent magnetization. For each spin valve, four absorption spectra were collected, With the remanent magnetization initially parallel to the incident beam direction, a pair of spectra were recorded, one with the helicity of the incident photons parallel to the remanent magnetization of the device, and one with their helicity antiparallel to the remanent magnetization. Next, the samples were rotated in order to align their remanent magnetization antiparallel to the incident beam direction, and a pair of absorption spectra was similarly obtained from beams polarized with opposite helicity. Finally, each absorption spectrum was normalized to the incident photon flux.