Fe/MnAs bilayers: Magnetic anisotropy and the role of the interface

We have studied different aspects of the magnetic behavior of Fe(5 nm)/MnAs(100 nm) bilayers epitaxially grown on GaAs(1 0 0). Ferromagnetic resonance (FMR) measurements were performed in order to characterize the magnetic anisotropies of the films and the interlayer coupling between them. The chemical composition of the interface was investigated by X-ray photoemission spectroscopy (XPS). The iron layer FMR spectrum is highly temperature dependent between 280 K and 320 K as its parameters are strongly altered in the α/β phase coexistence regime of the MnAs layer, revealing a strong interlayer coupling in this T-region. Additionally, the XPS experiments demonstrate the existence of an Fe-MnAs intermixed interface. This result would explain the appearance of an additional uniaxial anisotropy in the plane of the Fe films, together with a strong reduction in its magnetocrystalline anisotropy and a negligible direct exchange coupling in the MnAs ferromagnetic state.