Effect of magneto-structural phase coexistence in MnAs on the magnetic behavior of MnAs/Fe bilayers

In this work we present a magneto-structural study of MnAs/Fe bilayers, epitaxially grown on GaAs(1 0 0). The coexistence of ferromagnetic and non-magnetic phases is observed by scanning tunneling microscopy (STM) at room temperature. The magnetic force microscopy (MFM) images of the samples show a stripe-patterned domain structure. The magnetization reversal at the coercive field is observed at MFM micrographs measured at different fields. The temperature dependence of the ferromagnetic resonance (FMR) spectra allows us to follow the evolution of the phase coexistence up to the Curie temperature. Two main lines can be identified in the FMR spectra in the phase coexistence region: one of them is associated to the FMR of the Fe layer. The other one, near 3000 Oe, could be associated to the resonance of Mn ions. The general appearance of the FMR spectra is strongly temperature dependent. The resonance field, line width, and shape of the Fe line is strongly altered in the α and β coexistence region, where a severe drop of the resonance field is observed. The temperature dependence of the iron resonance nicely follows the transition of the underlying MnAs layer