University of Minnesota
School of Physics & Astronomy

Quantum Materials Seminar

Wednesday, May 8th 2019
Speaker: Turab Lookman
Subject:  Vortex structures in ferroelectric nanoparticles

There has been much interest in topological defects of spontaneous polarization as templates for unique physical phenomena and in the design of electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. I will discuss the behavior of three-dimensional vortices formed due to competing interactions involving ferroelectric domains observed by Bragg coherent diffractive imaging. I will show results for a single BaTiO3 nanoparticle of size ~100 nm in a composite polymer/ferroelectric capacitor, and discuss the structural phase transitions under the influence of an external electric field, including a mobile vortex core exhibiting a reversible hysteretic transformation path and changes in toroidal moment. Results and extensions to Barium Hexaferrite, as well as some recent results on observations of skyrmions in YIG, will be pointed out. Time permitting, I will also discuss the observation of very large magnetostrictive coefficients in nanowires.

Faculty Host: Martin Greven

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