Magnetoelectric bilayer and multilayer structures of magnetostrictive and piezoelectric oxides

Materials capable of field conversion, from magnetic to electric or vice versa, are of fundamental and technological importance. We report a giant magnetoelectric (ME) effect that results from stress-mediated electromagnetic coupling in bilayers and multilayers of nickel ferrite and lead zirconate titanate. Samples with layer thickness 10--200 \ensuremath{\mu}m were synthesized by doctor-blade techniques. The magnetoelectric voltage coefficient ${\ensuremath{\alpha}}_{\mathbf{E}}$ ranges from 460 mV/cm Oe in bilayers to 1500 mV/cm Oe for multilayers. The transverse effect is an order of magnitude stronger than longitudinal ${\ensuremath{\alpha}}_{\mathbf{E}}.$ The ME coefficient is maximum at room temperature and a general increase in ${\ensuremath{\alpha}}_{\mathbf{E}}$ is observed with increasing frequency. Data on the dependence of ${\ensuremath{\alpha}}_{\mathbf{E}}$ on volume fraction of the two phases and bias magnetic field are in excellent agreement with a theoretical model for a perfectly bonded bilayer.