Download or read book The Magnetoelectric Effect in Oxide Thin Film Heterostructures written by Julian Irwin and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetoelectric materials are poised to make a technological impact in a world where improving efficiency and performance of electronics is increasingly important. That magnetoelectric effect is coupling of electrical and magnetic orderings provided by a single material or several coupled materials. This dissertation explores magnetoelectric effects in two different oxide thin film heterostructures. First, the intrinsic magnetoelectric effect in room temperature multiferroic bismuth ferrite (BiFeO[subscript 3]), and second the extrinsic magnetoelectric effect in strain-coupled composite membranes. Bismuth ferrite is one of the few intrinsically magnetoelectric materials with possible technological importance, as it is ferroelectric and antiferromagnetic at room temperature. Exploiting multiferroic BiFeO[subscript 3] thin films in spintronic devices requires deterministic control of both internal magnetoelectric coupling in BiFeO[subscript 3], as well as exchange coupling of its antiferromagnetic order to a ferromagnetic overlayer. We present an approach using a monodomain magnetoelectric state with single-step switching. Here we demonstrate room temperature, deterministic and robust, exchange coupling between monodomain BiFeO[subscript 3] films and a Co overlayer that is intrinsic (i.e., not dependent on domain walls). Direct coupling between BiFeO[subscript 3] antiferromagnetic order and Co magnetization is observed, with ~ 90[degrees] in-plane Co moment rotation upon single-step switching that is reproducible for hundreds of cycles. Magnetoelectricity in piezoelectric / ferromagnetic thin-film heterostructures comes from piezoelectric strain combined with magnetostriction. In-plane magnetization rotation with an electric field across the film thickness has been challenging due to the large reduction of in-plane piezoelectric strain by substrate clamping, and in two-terminal devices, the requirement of anisotropic in-plane strain. Here we show that these limitations can be overcome two different ways in thin films. First by designing the piezoelectric strain tensor using the boundary interaction between biased and unbiased piezoelectric in (001)-oriented [Pb(Mg[subscript 1/3]Nb[subscript 2/3])O[subscript 3]][subscript 0.7]-[PbTiO[subscript 3]][subscript 0.3] (PMN-PT) membranes with ferromagnetic Ni overlayers, and second by fabricating (011)-oriented Ni/PMN-PT membranes capable of generating anisotropic strain from the symmetry of the crystal alone. We demonstrate several magnetoelectric effects including 90[degrees] rotation of in-plane magnetic anisotropy with a perpendicular electric field. Further optimization of magnetoelectric PMN-PT membrane heterostructures is expected to allow for magnetization rotation at even lower voltages and for nonvolatile magnetoelectric switching.