  Strain-mediated magnetoelectric (ME) coupling in ferroelectric (FE) /
ferromagnetic (FM) heterostructures offers a unique opportunity for both
fundamental scientific research and low power multifunctional devices.
Relaxor-ferroelectrics, like (1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PMN-xPT), are
ideal FE layer candidates due to their giant piezoelectricity. But thin films
of PMN-PT suffer from substrate clamping which substantially reduces
piezoelectric in-plane strains. Here we present the first demonstration of low
voltage ME coupling in an all-thin-film heterostructure which utilizes the
anisotropic strains induced by the (011) orientation of PMN-PT. We completely
remove PMN-PT films from their substrate and couple with FM Ni overlayers to
create membrane PMN-PT/Ni heterostructures showing 90 degree Ni magnetization
rotation with 3V PMN-PT bias, much less than the bulk PMNPT ~100V requirement.
Scanning transmission electron microscopy and phase-field simulations clarify
the membrane response. These results provide a crucial step towards
understanding the microstructural behavior of PMN-PT thin films for use in
piezo-driven magnetoelectric heterostructures.
