Professor Liuyan Zhao was recently awarded a three-year Young Investigator Research Program award through the U.S. Air Force. These awards aim to foster creative basic research in science and engineering, enhance early career development of outstanding young investigators, and increase opportunities for the young investigators to recognize the Air Force mission and the related challenges in science and engineering. Professor Zhao’s proposed research, “Realizing and controlling unconventional magnetic excitations in non-Bravais magnets,” was one of only 40 recent awards.
Magnetism, although familiar in the context of a permanent magnet, encompasses an extremely broad class of physical systems. All types of magnetic characteristics arise from a property of electrons called spin. Spin can be visualized like a spinning top that has an axis with a north and south pole. A tiny magnet, called a “magnetic dipole,” forms between the north and south pole. The orientation of these magnetic dipoles within a material is the basis for everything from permanent magnets to the “non-Bravais” magnets Professor Zhao plans to study.
One way to visualize conventional magnetic systems, like permanent magnets, is to think of a sheet of graph paper with a magnetic dipole on the corner of every square. When all the dipoles point in the same direction, a permanent magnet or “ferromagnet” is formed. A related type of magnetism, called antiferromagnetism, occurs when magnetic dipoles alternate their direction. In the graph paper analogy, every other dipole would point toward the top of the paper, and the rest would point toward the bottom of the paper.
Non-Bravais magnets can have similar patterns in their magnetic dipoles, but their underlying grid is different. Instead of squares, the dipoles might be at the corners of every hexagon in a honeycomb shape, known as a honeycomb magnet. Another possible pattern is the kagome magnet, where magnetic dipoles are at every corner of an interlocking pattern of hexagons and triangles. These non-Bravais grids not only influence the type of magnetic property that can be present in a material, they can also lead to the emergence of robust topological magnetic properties.
Professor Zhao plans to study these materials using optical spectroscopy and microscopy techniques. Current research goals include detecting and manipulating the physical characteristics of non-Bravais magnets. However, future applications of this work are in spin-based electronics, or spintronics, which could provide a faster alternative to electronics currently in use today. Much of the research into spintronics has been done using ferromagnets, however, non-Bravais magnets have the potential to be even more fruitful because of the topological magnetic properties that emerge.
Professor Liuyan Zhao