Investigation of anisotropy by ferromagnetic resonance (FMR) in exchange-coupled bilayer films

We have used ferromagnetic resonance (FMR) to investigate magnetic anisotropy in bilayer exchange-coupled thin films. Experiments, using both our 9 and 33 GHz FMR spectrometers, were done on two systems: NiFe/FeMn and NiFe/α-Fe2O3. In some of the NiFe/α-Fe2O3specimens an additional response was detected at 33 GHz. We attribute this additional resonance to a region formed by interdiffusion of NiFe and α-Fe2O3at their common interface. Effective anisotropy field, g-value and the relative volume have been determined for each ferromagnetic region. Auger profile, TEM and CBED (convergent beam electron diffraction) cross-section examinations were performed for an interdiffused specimen, the results are consistent with the presence of a layer containing Fe and Fe3O4located between the NiFe and α-Fe2O3regions. A memory effect, due presumably to irreversible spin reorientation at the interface, was observed in some of the NiFe/α-Fe2O3specimens.