Noncollinear coupling of iron layers through native iron oxide spacers

We have found a magnetic superstructure in multilayers that consist of iron and its native oxide. Employing nuclear resonant scattering of synchrotron radiation from ⁵⁷Fe probe layers, this manifests as $1∕2$-order Bragg peaks in the reflectivity curve. From the field dependence of their intensity, we deduce the existence of two magnetic sublattices that are canted by an angle of almost 90^∘{} and rotate as one unit in low fields. For higher fields, the two sets of moments gradually align collinear to the external field. This behavior can be explained by a coupling of two adjacent Fe layers that is mediated by an antiferromagnetic order in the oxide spacer between them.