Spin alignment of surface oxidized CoxNi1–x/Cu(001)

We investigated the ferromagnetic (FM)/antiferromagnetic (AF) spin alignment of a 13 monolayer oxidized CoxNi1–x/Cu(001) (x = 0 or 0.05) surface by X-ray magnetic circular dichroism and X-ray magnetic linear dichroism photoemission electron microscopy (XMCD-PEEM and XMLD-PEEM). Surface NiO and the underlying Ni (CoxNi1–x) were found to be AF and FM by analyzing the gray scale of XMLD-PEEM and XMCD-PEEM images; this indicates the spin orientation with respect to the polarization of the incident X-ray. We found both collinear and perpendicular alignment of the FM and AF spins. This suggests that the AF NiO is magnetically random, resulting in coercivity enhancement without exchange bias in the surface-oxidized CoxNi1–x/Cu(001) films.