Multiferroic materials that demonstrate magnetically driven ferroelectricity have fascinating properties such as magnetic (electric) field-controlled ferroelectric (magnetic) response that can be used in transformative applications including fast-writing, power-saving, and nondestructive data storage technologies in next-generation computing devices. However, since multiferroicity is typically observed at low temperatures, it is highly desirable to design multiferroic materials that can operate at room temperature. I will show that BaFe12O19 is a promising room-temperature multiferroic material, and we unravel in 3D the dynamics of topological defects, strain and improper ferroelectric domains driven by electric fields in individual BaFe12O19 nanocrystals. Using Bragg Coherent Diffractive Imaging in combination with grouptheoretical analysis, first-principles density functional calculations of phonons and Landau phase-field theory we uncover in 3D the dynamics of topological defects, strain and improper ferroelectric domains driven by electric fields in individual BaFe12O19 nanocrystals. Our results show that BaFe12O19 is an improper ferroelectric, in contrast to the current paradigm that adheres to the absence of improper ferroelectricity. Moreover, the fine structure of the reconstructed Bragg electron density suggests that BaFe12O19 may be ableto harbor novel topological quantum states of matter and a pathway to transform information technologies.
Dr. Edwin Fohtung received his PhD. (Dr. rer. nat., summa cum laude) in Materials Science & Physics from the Univ. of Freiburg, Germany in 2010. He obtained his B.Sc. and M.Sc. in Technical and Applied Physics from the Loffe Institute, St. Petersburg State Polytechnic Univ., Russia in 2007. He was employed as a scientific staff (doktoranden Wissenschaftliche Mitarbeiter) from 2007 to 2010 at the ANKA National Synchrotron Light Source Facility of the Forschungszentrum Karlsruhe in Germany. Edwin was a postdoctoral fellow in the Physics Dept. at UC San Diego. He was recently promoted to the LANSCE Associate Professor of physics and materials at New Mexico State Univ. and Los Alamos National Laboratory. One of his research interess is in the studies of ferroic nanostructures where charge, spin, lattice and orbital degree of freedom compete to create novel topological configurations of electric and magnetic polarization. He primarily develops scattering and imaging techniques using photons and neutrons to interrogate nanoscale device materials. He is the recipient of numerous awards including the Rosen Fellow at LANL and serves on various committees. He is also the recipient of multiple DOD-AFOSR, AFRL, National Nuclear Security Administration (NNSA) grants and other LANL laboratory directed research and development program awards. Dr. Fohtung is currently a visiting professor at Lund University, and a LINX (Lund Institute of Advanced Neutron and X-ray Science) fellow in Sweden.