Magnetic circular dichroism study of Fe/Co/Cu (001) using electron yield x-ray absorption spectroscopy with different probe depths

Abstract

To obtain depth-resolved magnetic information from Fe films grown on fcc CoCu (001), we have used various signal sources for the detection of x-ray absorption spectroscopy. These include total electron yield (TEY) and partial electron yield (PEY) of inelastic electrons at various kinetic energies between 70 and 470 eV as well as PEY using photoelectrons at a fixed binding energy (constant initial state: CIS) near the Fermi level. Inelastic electron yield at electron emission angles up to 87° from the surface normal was found to be as nonsurface sensitive as TEY, however, the CIS mode shows a shorter information depth, comparable to the inelastic mean free path of photoelectrons. No difference in the dichroic signal at the Fe L3 edge was found between the CIS and TEY modes for a 2-monolayer (ML) FeCo film, but an 8-ML FeCo film showed a much higher dichroic signal in the CIS mode than that in the TEY mode. This is consistent with a homogeneous magnetic film at an Fe thickness of 2 ML and a nonhomogeneous magnetic film with a live ferromagnetic layer on the surface with nonferromagnetic underlayers at an Fe thickness of 8 ML. Thus, it is possible to extract depth-resolved magnetic information from x-ray magnetic circular dichroism by combining the surface sensitive CIS mode with other detection modes with less surface sensitivity. © 2005 American Institute of Physics.