Magnetoelectric, pinning and depinning properties in Pb(Zr0.5Ti0.5)O3/Fe3O4 composite films

The magnetoelectric (ME) coupling effect was demonstrated in sol-gel deposited Pb(Zr,Ti)O-3 films embedded by Fe3O4 nanoparticles. The polarization-field hysteresis curves show 'pinched' shapes at room temperature and higher frequencies, whereas they display normal square-like loops at 150 degrees C and frequencies lower than 0.5 Hz. Our data confirm that the pinched loop can be relaxed after the Pb(Zr,Ti)O-3/Fe3O4 composite films are poled magnetically, and an anisotropic magnetoelectric (ME) coupling effect is demonstrated. Analysis of the dc voltage dependence of the dielectric response indicates two peaks of dielectric constant loops for each half cycle at lower temperatures and bias voltages, which are different from the butterfly shape for normal ferroelectrics. Nevertheless, the normal butterfly hysteresis loops are presented at 360 K and at a bias voltage level of 25 V. The occurrence of pinched polarization-voltage loops and two peaks of dielectric constant curves for each half cycle may be attributed to the unintentional doping of iron ions in Pb(Zr,Ti)O-3/Fe3O4 composite films.