Low frequency and Microwave Magnetoelectric Effects in Thick Film Heterostructures of Lithium Zinc Ferrite and Lead Zirconate Titanate

Magnetoelectric (ME) coupling at low frequencies and at x-band have been investigated in layered samples containing zinc substituted lithium ferrite and lead zirconate titanate (PZT). Multilayers of Li0.5-x/2ZnxFe2.5-x/2O4 (LZFO) (x=0-0.4) and PZT were prepared by lamination and sintering of thick films. At low frequencies (10-1000 Hz), the ME voltage coefficient for transverse fields is higher than for longitudinal fields. With Zn substitution in the ferrite, transverse coupling increases to a maximum for x=0.3 and then decreases for higher x. Analysis based on our model for a bilayer implies an efficient magneto-mechanical coupling with Zn substitution, resulting in strong ME interactions. Microwave ME coupling is studied through measurements of shift in the ferromagnetic resonance field due to an applied electric field. Estimated ME constants from such data are in agreement with our model for a ferrite-PZT bilayer.Comment: To be published in Solid State Communication

Theory of low frequency magnetoelectric coupling in magnetostrictive-piezoelectric bilayers

A theoretical model is presented for low-frequency magnetoelectric (ME) effects in bilayers of magnetostrictive and piezoelectric phases. A novel approach, the introduction of an interface coupling parameter k, is proposed for the consideration of actual boundary conditions at the interface. An averaging method is used to estimate effective material parameters. Expressions for ME voltage coefficients are obtained by solving elastostatic and electrostatic equations. We consider both unclamped and rigidly clamped bilayers and three different field orientations of importance: (i) longitudinal fields in which the poling field, bias field and ac fields are all parallel to each other and perpendicular to the sample plane; (ii) transverse fields for magnetic fields parallel to each other and perpendicular to electric fields, and (iii) in-plane longitudinal fields for all the fields parallel to each other and to the sample plane. The theory predicts a giant ME coupling for bilayers with cobalt ferrite (CFO), nickel ferrite (NFO), or lanthanum strontium manganite (LSMO) for the magnetostrictive phase and barium titanate (BTO) or lead zirconate titanate (PZT) for the piezoelectric phase.Comment: To be published in Physical Review B, August 1, 200