Electric-field controlled magnetic reorientation in exchange coupled CoFeB/Ni bilayer microstructures

A novel strain-mediated composite multiferroic system is investigated in this work. The system is composed of magnetostrictive microstructures made of a ferromagnetic bilayer of negative magnetostrictive Ni and positive magnetostrictive CoFeB fabricated on a ferroelectric Pb(Mg1/3Nb2/3)0.69Ti0.31O3 (PMN-PT) single crystal substrate. When an electric field is applied across the PMN-PT substrate, magnetization reorientation occurs in the microstructures that are predominantly initialized into flux-closure states. An x-ray magnetic circular dichroism-photoemission electron microscope is used to experimentally visualize the electrically induced changes of the magnetization state of the individual layers as well as the exchange coupling between the two layers. Such heterostructures with tunable magnetoelectric properties have potential for new magnetic memory and sensor applications.