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 $\delta H_E$ in the resonance field for the ferromagnet. The strength of ME coupling is obtained from data on $\delta H_E$ vs $E$. Studies were performed at $9.3\mathrm{GHz}$ 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 $E=0–8\mathrm{kV}∕\mathrm{cm}$ 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 $1–5.4\mathrm{Oe}\mathrm{cm}∕\mathrm{kOe}$, 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.

Figure 1

Ferromagnetic resonance (FMR) at $9.3\mathrm{GHz}$ in a bilayer of (111) yttrium iron garnet (YIG) on gadolinium gallium garnet (GGG) substrate and (001) lead magnesium niobate-lead titanate (PMN-PT). A 13.2 micron thick YIG film and $0.5\mathrm{mm}$ thick PMN-PT were used. The profiles of absorption vs static magnetic field $H$ are shown for a series of electric field $E$ applied to the bilayer and for $E$ and $H$ applied perpendicular to the bilayer plane and parallel to $⟨111⟩$ axis of YIG. The profiles show an increase in the resonance field with $E$.

Figure 2

(Color online) Microwave magnetoelectric effect at $9.3\mathrm{GHz}$ in bilayers of (111) YIG-(001) PMN-PT. The shift in the resonance field $\delta H_E$, measured from profiles as in Fig. 1, is shown as a function of $E$ for a series of YIG film thickness. The lines are linear fit to the data.

Figure 3

(Color online) Measured field shift at $E=8\mathrm{kV}∕\mathrm{cm}$ as a function of YIG-to-PMN-PT volume ratio for in-plane and out-of-plane $H$. The lines are guide to the eye.

Figure 4

(Color online) Comparison of theory (lines) and data on the ME constant $A$ for in-plane (circles) and out-of-plane (squares) $H$. The $A$-values are shown as a function of ratio of volumes of (YIG+GGG) and PMN-PT.