Ferroelectric polarization changes local structure at complex oxide interfaces
- PDF / 239,089 Bytes
- 1 Pages / 585 x 783 pts Page_size
- 72 Downloads / 252 Views
Ferroelectric polarization changes local structure at complex oxide interfaces
B
y coupling an electron’s charge and spin, spintronic memories could transport information at a much faster rate than conventional computer memories. A unique way of making a spintronic memory is by using a magnetoelectric material—a material with magnetic properties that can be controlled by an electric field. One way to make this type of materials system is by alternating layers of ferromagnetic and ferroelectric materials. However, any variations in the electronic and magnetic phases at the layer interface could affect the transport process. A recent report in Nature Communications (DOI:10.1038/ncomms7735) explores such local variations at the atomic scale in order to understand asymmetries at such interfaces. Interestingly, the team, led by Mitra Taheri of Drexel University, found that the polarization is not uniform throughout the film, but instead has unique local structure. Controlling a material’s magnetic properties “is the key for new spintronic devices,” says Evgeny Tsymbal, George Holmes University Distinguished Professor of Physics and Astronomy at the University of Nebraska–Lincoln, who was not involved in this work. “There are a number of industrial companies that are interested in controlling magnetism by electric fields. It’s a big deal now, but there aren’t yet any spintronic devices based on this.” Further understanding of the mechanism driving spin transport is needed before researchers can consider industrial applications. “The science is important, because if we understand the underlying mechanism then we can fabricate relevant structures, explore different kinds of materials, and improve their properties so that eventually we will come to the devices.” The first layer of the materials system in the present work consisted of a manganese perovskite oxide, specifically La0.7Sr0.3MnO3 (LSMO). In this material, valence electrons from the 3d orbital of the Mn atoms are delocalized and can
be used to transmit spin information. Layering LSMO with a ferroelectric material, specifically PbZr 0.2Ti 0.8O 3 (PZT), polarizes the electron spin when an electric current is passed through the nanoscale composite. A final layer of LSMO completes the circuit, so that the bottom layer is in a hole accumulation state while the top layer is in a hole depletion state. An interesting aspect of this system is that the magnetic properties may be controlled by an exter- High-angle annular dark-field scanning transmission electron nal electric field. Because microscope image of the transition from LSMO to PZT (bottom left to top right). Localized polarization occurs at manganese valence elec- the LSMO/PZT interface due to the ferroelectric properties trons are used in spin of the PZT layer. Credit: James Rondinelli. transport, changing the valence will alter the material’s magnetoelectric properties. Typically, a chemical change At the interface of LSMO and PZT, is used to alter the valence structure; for exresearchers observed a gradient
Data Loading...
