Influence of a non-magnetic underlayer on the magnetic anisotropy of ultra-thin Co sandwiches

We have used in situ polar Kerr effect measurements to study the magnetic anisotropy of MBE-grown Cu/Au/Co/Au sandwich structures. We reported earlier that the magnitude of the Au/Co/Au perpendicular anisotropy is strongly peaked at ~1 atomic layer Au overlayer coverage. We report here extensions of this work to investigate the influence on anisotropy of a confined ultra-thin non-magnetic underlayer placed at one of the Co interfaces. Sandwich structures were deposited in a stepped-wedge geometry providing multiple underlayer thicknesses for each sample. For the case of an underlayer wedge of Au, e.g. Cu/Au(x)/Co/Au, we find a sharp minimum in the perpendicular anisotropy at ~1 atomic layer of Au. This anisotropy behavior is opposite to that of a Au overlayer deposited on a Co film