MSE Fall Seminar Series: Lucas Caretta, UC Berkeley
Description
Manipulating Noncolinear Textures in Ferroic Oxides
Lucas Caretta - UC Berkeley
The ability to control and manipulate ferroic order in condensed matter systems has tremendous scientific interest and many potential technological applications. Fundamentally, excitations in these systems, such as domain walls, cycloids, and skyrmions, provide a rich playground for studying intriguing physical phenomena, including chirality, inversion symmetry, spin-orbit coupling, and magnetoelectric coupling. Additionally, ferroic systems and their noncolinear excitations hold vast potential to encode bits of information for next-generation memory and logic. One technological and scientific challenge has been the stabilization of small ferroic bits and noncolinear textures and efficient manipulation of them with high speeds. This is critical for dense, power-efficient, and fast memory and logic. Here, we show two examples in which synthesizing oxide-based heterostructures helps to overcome fundamental limitations hindering progress in ferroic technologies and opens arenas for new fundamental materials physics.
First, by using a combination of epitaxial growth techniques, interface design1, and magnetic sublattice engineering2, we stabilize 10 nm skyrmion bits at room temperature2 and drive magnetic domain walls to velocities over 4,300 m/s3, providing a new platform to study complex fundamental phenomena like topology, inversion symmetry, and even relativistic dynamics. Second, using a confined layer of BiFeO3 (BFO) as a model system, we stabilize mixed-phase coexistence of emergent centrosymmetric and non-centrosymmetric BFO phases with insulating antipolar order and semiconducting polar order, respectively4. Moreover, we use electric fields to interconvert between these two phases, resulting in colossal changes in the non-linear optical response of over three orders of magnitude and a change in resistivity of over five orders of magnitude4. Not only does this work push the frontiers of materials growth and design, it also utilizes a suite of advanced electrical, optical, and magnetic in-situ characterization techniques and develops new ones3,4,5.
1. Caretta, L. et al. Interfacial Dzyaloshinskii-Moriya Interaction Arising from Rare-Earth Orbital Magnetism in Insulating Magnetic Oxides. Nat. Commun. 11, 1090 (2019).
2. Caretta, L. et al. Fast Current-Driven Domain Walls and Small Skyrmions in a Compensated Ferrimagnet. Nat. Nanotechnol. 13, 1154–1160 (2018).
3. Caretta, L. et al. Relativistic Kinematics of a Magnetic Soliton. Science 1442, 1438–1442 (2019).
4. Caretta, L. et al. Nonvolatile Electric Field Control of Inversion Symmetry. in preparation. (2021).
5. Caretta, L. et al. All-Optical Motion of Chiral Domain Walls and Skyrmion Bubbles. under review. (2021).