ABSTRACT

This chapter dwells on distinctive features of magnetoelectric (ME) interactions in ferrite-PZT nanobilayers at low frequencies and in electromechanical resonance and ferromagnetic resonance regions. The models take into account the clamping effect of substrate, flexural deformations, and the contribution of lattice mismatch between composite phases and substrate to ME coupling. Lattice mismatch effect has been taken into account by using the classical Landau-Ginzburg-Devonshire phenomenological thermodynamic theory. The strength of low-frequency ME interactions is shown to be weaker than for thick film bilayers due to the strong clamping effects of the substrate by giving the example of NFO-PZT nanobilayer on SrTiO3 substrates. However, flexural deformations result in the considerably lower rate of change of ME voltage coefficient with substrate thickness compared to the case when neglecting the flexural strains. To avoid the strong clamping effects of the substrate, nanopillars of a magnetostrictive material in a piezoelectric matrix can be used as an alternative. For nanopillars of NFO in PZT matrix

on MgO, the substrate pinning effects are negligible when the length of the pillar is much greater than its radius. Nanostructures in the shape of wires, pillars, and films are important for increased functionality in miniature devices [4]. A

model of the static magnetoelectric (ME) effects in BaTiO3-CoFe2O4 nanopillars and nanobilayers was considered in Chapter 4. However, a fundamental understanding of the size and shape-dependent characterization of the ME effect in composites, particularly down to nanoscale dimensions, is presently lacking. An improved knowledge of the nanoscale ME properties will help achieve miniaturization of potential ME devices.