Microcharacterization of the surface oxidation of Py/Cu multilayers by scanning X-ray absorption spectromicroscopy

The local surface oxidation of the permalloy Surface layer in Py/Cu GMR mul tilayers on a micron lateral scale has been analyzed by means of a microspo t-X-ray absorption spectromicroscope utilizing synchrotron radiation from t he Advanced Light Source bending magnet beamline 6.3.2. Additionally, the G MR multilayer samples prepared by do magnetron sputtering have been analyze d by cross-sectional transmission electron microscopy, hard X-ray reflectio n and magnetoresistance measurements. The formation of a passivating iron-o xide layer on the sample surface was identified by X-ray absorption near ed ge structure spectroscopy (XANES) near the Fe-2p edge while no indication f or nickel-oxide formation could be found. Small micron-size pits of reduced iron-oxide concentration could be identified by XANES microscopy while the corresponding nickel distribution appeared to be homogeneous. The results are explained in terms of a local breakdown of the passivating oxide layer.