PAMS Seminar: "Designer Magnet with Fundamental and Practical Implications" by Dr. Deepak Singh

Dr. Deepak Singh
Department of Physics & Astronomy
University of Missouri

Abstract:
Magnetic honeycomb lattice is a highly intriguing physical system, which has drawn lot of attention in both the bulk and the two-dimensional nanostructured specimens. Study of the artificially designed nanoscopic honeycomb lattice, artificial honeycomb spin ice, is argued to unravel many novel facets of topological magnetic charge physics. In addition to the inherent geometrical frustration, the competing nature of exchange interactions (J1, J2 terms) in thermally tunable artificial magnetic honeycomb lattice renders a disorder-free environment for the exploration of new quantum mechanical phenomenon or gorund state. Our research has revealed the development of highly unexpected magnetic charge liquid state in the quasi-classical system. The magnetic charge liquid state is characterized by the massively degenerate ground state of magnetic charges that remain unperturbed to high magnetic field application, and a perpetual dynamic state in the absence of thermal fluctuation at low temperature. Typically, the dynamic process in a nanostructured magnet is mediated by the finite size domain wall motion, which requires magnetic field or electric current application. Contrary to this notion, the dynamic state in 2D magnetic honeycomb lattice is owed to the self-propelled magnetic charge kinetics with very fast relaxation rate, ~ 20 ps. Such relaxation rate is typically found in bulk material of atomistic origin. It leads us to argue that the magnetic charge is a quantum mechanical ‘macroscopic’ quasi-particle entity, which was never envisaged before. The new finding can have strong implication to the spintronics research, as evidenced from the recently demonstrated magnetic diode effect due to magnetic charge mediation in permalloy honeycomb lattice.

Free