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Strain-mediated magnetoelectric coupling in magnetostrictive/piezoelectric heterostructures and resulting high frequency effects

Magnetoelectric coupling terms are derived in piezoelectric/magnetostrictive (multiferroic) thin film heterostructures using Landau-Ginzburg free energy expansions in terms of strain and by considering strain boundary conditions between the two materials. Then, a general effective medium method for solving for the complete electromagnetic susceptibility tensor of such heterostructures is used to calculate the ferromagnetic resonance frequency in a BaTiO$_3$/NiFe$_2$O$_4$ superlattice. This method differs from existing methods for treating magnetoelectric heterostructures since the magnetic and electric dipolar fields are not assumed constant but vary from one film to another. The ferromagnetic resonance frequency shift is calculated as a function of applied electric field and is compared to some experimental results.