IUP alumna Dr. Jennifer Sloppy (B.S. ’03) will visit the Department of Chemistry on Friday, September 16, 2011, to speak with faculty and students before presenting “Oxide Thin Films for Multiferroic Applications Studied by Transmission Electron Microscopy.”
Dr. Sloppy received her Ph.D. in Materials Science and Engineering from Penn State in 2009 and is currently a post-doctoral student at Drexel University in the Department of Materials Science and Engineering.
Her presentation will be given during the department’s seminar series in Weyandt Hall, room 240, from 3:35 to 4:25 p.m. All are welcome to attend, and light refreshments will be served.
Multiferroic materials simultaneously exhibit two or more of the following properties: ferroelectricity, ferromagnetism, ferroelasticity, antiferroelectricity, or antiferromagnetism. The ability to control magnetic ordering via an applied bias would provide a broad field for innovation and impact such technologies as high-density ferroelectric and magnetoresistive memories, spintronics devices, and magnetic field sensors.
Extrinsic multiferroic devices can be fabricated by layering ferroelectric and ferromagnetic materials; this type of heterostructure may permit rapid control of magnetic domain orientation via an applied electric field. In the case of layered thin films of ferromagnetic La0.67Sr0.33MnO (LSMO) on ferroelectric Pb0.20Zr0.80TiO3 (PZT), magnetoelectric coupling occurs via a strain-mediated mechanism. Strain also plays a vital role in determining the concentration and type of interfacial defects and the nucleation, propagation, growth, and hysteresis behavior of magnetic domains. The strain in the LSMO and at the PZT/LSMO interface is varied by changing the thickness of the PZT layer, and the direction of polarization in the PZT is varied by choosing either an LSMO or a SrRuO3 (SRO) underlayer. Bulk magnetic properties are measured using vibrating sample magnetometry (VSM) and correlated with atomic-level structure and chemistry measured by scanning transmission electron microscopy (STEM) in an aberration corrected microscope. This technique allows for the simultaneous collection of Z-contrast images and electron energy loss spectra (EELS) with a spatial resolution of 60 picometers.
Bismuth ferrite (BiFeO3) is an intrinsic multiferroic that is simultaneously ferroelectric and antiferromagnetic. The formation and relaxation of sub-micron ferroelectric domains is reported via in-situ biasing in the TEM. The kinetics of domain wall motion and a variety of dynamic behaviors, such as domain wall collisions, domain attraction and repulsion, and domain-defect interactions are observed. In-situ TEM experiments have demonstrated the observation of domain wall motion at unprecedented temporal and spatial resolutions.