  Magnetoelectric interactions in bilayers of magnetostrictive and
piezoelectric phases are mediated by mechanical deformation. Here we discuss
the theory and companion data for magnetoelectric (ME) coupling at
electromechanical resonance (EMR) in a ferrite-lead zirconate titanate (PZT)
bilayer. Estimated ME voltage coefficient versus frequency profiles for nickel,
cobalt, or lithium ferrite and PZT reveal a giant ME effect at EMR with the
highest coupling expected for cobalt ferrite-PZT. Measurements of resonance ME
coupling have been carried out on layered and bulk composites of nickel
ferrite-PZT. We observe a factor of 40-600 increase in ME voltage coefficient
at EMR compared to low frequency values. Theoretical ME voltage coefficients
versus frequency profiles are in excellent agreement with data. The resonance
ME effect is therefore a novel tool for enhancing the field conversion
efficiency in the composites.
