Magnetoelectric Coupling in Complex Oxide Heterostructures

Current efforts to use materials with multifunctional capabilities have renewed interest in multiferroics, which display a coupling between ferroic order parameters. Engineered structures that combine dissimilar magnetic and ferroelectric systems epitaxially have been shown to exhibit enhanced magnetoelectric coupling. In this work, off-axis RF magnetron sputtering was used to deposit epitaxial ferroelectric Pb(Zr,Ti)O$_3$ (PZT) / La$_{0.8}$Sr$_{0.2}$MnO$_3$ (LSMO) heterostructures with high crystalline quality and atomically smooth surfaces. X-ray diffraction shows c-axis oriented growth of PZT, with a typical root-mean-square (RMS) surface roughness of ~5\AA. We employ magneto-optic Kerr effect (MOKE) magnetometry to study directly the local magnetic state of the LSMO as a function of the PZT polarization state. We demonstrate direct control of magnetism via applied electric fields, including on/off switching of magnetism. The coupling between magnetic and electric order parameters in ferroelectric / Sr-doped lanthanum manganite heterostructures is illustrated by hysteretic M-E (magnetization vs. electric field) loops, with a measured magnetoelectric susceptibility of $\alpha \sim 1 $Oe cm / kV$^{-1}$.