Ferromagnetic resonance in the epitaxial system Fe/MgO/Fe with coupled magnetic layers

Temperature and thickness dependencies of ferromagnetic resonance (FMR) characteristics, such as resonance field, signal intensity, and linewidth have been studied at 9.25 GHz in both tunnel junctions MgO(100)/Fe1/MgO/Fe2/V and in single iron films MgO(100)/Fe/V having the same growth parameters as in junctions. The FMR data have been interpreted on the basis of structural and static magnetic measurements performed in this work, and compared with the known model of FMR in ultrathin magnetic layers coupled through a nonmagnetic spacer. An exponential decay of the coupling strength with spacer layers thickness together with the decrease of the coupling under film cooling found by the FMR, are in good agreement with the Slonczewski and Bruno theories developed for free electron spin polarized tunneling between the ferromagnetic layers across an insulating barrier.