Magneto-optic Kerr effect at the interface of Co/Gd bilayers

We have grown a set of crystalline Co/Gd(500 Å) bilayers on glass substrates with a Cr buffer layer by magnetron sputtering. The interface between Co and Gd has been investigated by Auger spectroscopy depth profiles, vibrating sample magnetometry (VSM) and magneto-optic Kerr effect (MOKE) on the air and glass sides of the sample at room temperature. The use of a Cr buffer with different thicknesses allowed us to probe the interface in MOKE measurements on the glass side. These show a small and reversed Kerr loop whereas those of the air interface are normal. Depth profiles indicate a wide interface ( ∼ 3–4 nm thick) in the Gd side that is partly oxidized. The results are discussed on the basis of polarization of interfacial spins or the effect of the oxygen contamination.