Microwave magnetoelectric effects in single crystal bilayers of yttrium iron garnet and lead magnesium niobate-lead titanate

The first observation of microwave magnetoelectric (ME) interactions through ferromagnetic resonance (FMR) in bilayers of single crystal ferromagnetic-piezoelectric oxides and a theoretical model for the effect are presented. An electric field $E$ produces a mechanical deformation in the piezoelectric phase, resulting in a shift $\ensuremath{\delta}{H}_{E}$ in the resonance field for the ferromagnet. The strength of ME coupling is obtained from data on $\ensuremath{\delta}{H}_{E}$ vs $E$. Studies were performed at $9.3\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ on bilayers of (111) yttrium iron garnet (YIG) films and (001) lead magnesium niobate-lead titanate (PMN-PT). The samples were positioned outside a ${\mathrm{TE}}_{102}$-reflection type cavity. Resonance profiles were obtained for $E=0--8\phantom{\rule{0.3em}{0ex}}\mathrm{kV}∕\mathrm{cm}$ for both in-plane and out-of-plane magnetic fields $H$. Important results are as follows. (i) The ME coupling in the bilayers is an order of magnitude stronger than in polycrystalline composites and is in the range $1--5.4\phantom{\rule{0.3em}{0ex}}\mathrm{Oe}\phantom{\rule{0.3em}{0ex}}\mathrm{cm}∕\mathrm{kOe}$, depending on the YIG film thickness. (ii) The coupling strength is dependent on the magnetic field orientation and is higher for out-of-plane $H$ than for in-plane $H$. (iii) Estimated ME constant and its dependence on volume ratio for the two phases are in good agreement with the data.