QSEC faculty collaborates with NIST, ANL and ORNL to discover a new topological magnetic state


QSEC member, Professor Nirmal Ghimire of GMU leads a group of materials science experts from Mason, NIST, ANL, and ORNL to discover a quantum phenomenon that has the potential to become a building block of future electronic technology emerges at high temperatures from a mechanism not before realized, the result of which is published on Science Advances, doi:10.1126/sciadv.abe2680.

Identification, understanding, and manipulation of novel magnetic textures are essential for the discovery of new quantum materials for future spin-based electronic devices. In order to find new ways to incorporate magnetic spins in the electronic devices for data storage and information processing, scientists have begun to explore spin textures in materials that can respond to external stimuli such as magnetic field. One of such phenomena is a topological Hall effect, where an electric charge flowing through a special spin texture is subjected to a deflecting force more than when it flows through a conventional magnet.

Dr. Nirmal Ghimire, assistant professor of physics, heads a collaboration with scientists from the National Institute of Standards and Technology (NIST), Argonne National Laboratory (ANL), and Oak Ridge National Laboratory (ORNL) that has identified a novel way in which increasing temperatures play a key role in forming a magnetic texture that generates the topological Hall Effect. The team studies the kagome-net magnet YMn6Sn6 by magnetometry, transport, and neutron diffraction measurements combined with first-principles calculations, identifies a number of nontrivial magnetic phases, explains their microscopic nature, and demonstrates that one of them hosts a large topological Hall effect (THE). A previously unidentified fluctuation-driven mechanism has been proposed, which leads to the THE at elevated temperatures. This interesting physics comes from parametrically frustrated interplanar exchange interactions that trigger strong magnetic fluctuations. According to Professor Ghimire, the results pave a path to chiral spin textures, promising for novel spintronics.

The research is funded by U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division.

For more information please see this article on Science Advances, the press release by GMU College of Science, or visit the Ghimire Research Group.