Ferromagnetic resonance in ferromagnetic/ferroelectric $Fe∕BaTiO3∕SrTiO3(001)$

Single Fe(001) films (⁠$30nm$ thick) have been epitaxially grown on ferroelectric $BaTiO3∕SrTiO3(001)$ substrates at different growth temperatures to study the mutual interaction between the multiferroic components. This paper reports on the as-grown magnetic properties of the structures as a precursor to a full investigation of the multiferroic interactions. Ferromagnetic resonance measurements were carried out at $36GHz$ cavity and variable frequency microstrip resonators. Dual resonance modes are observed in the film, which are attributed to relaxed Fe in the film interior and strained Fe at the interface. Fourfold anisotropy is present for both modes with energy density consistent with that of bulk Fe. The interface mode is characterized by a large out-of-plane anisotropy comparable and opposite in sign to the shape anisotropy. This strained interfacial Fe should serve to couple the multiferroic components in this system. Dispersion curves show both optic and acoustic branches along the hard axis [110], with the optic branch resulting from resonance below saturation, indicating high quality Fe in these samples. Growth temperature has minimal influence on the observed anisotropy energies.