Phys.org August 9, 2024
The indirect exchange interaction between local magnetic moments via surface electrons has been long predicted to bolster the surface ferromagnetism in magnetic topological insulators (MTIs), which facilitates the quantum anomalous Hall effect. This unconventional effect is critical to determining the operating temperatures of future topotronic devices. However, the experimental confirmation of this mechanism has not been investigated in intrinsic MTIs. An international team of researchers (University of Chicago, University of Florida, Pennsylvania State University, Israel) combined time-resolved photoemission spectroscopy with time-resolved magneto-optical Kerr effect measurements to explain the unique electromagnetism at the surface of an intrinsic MTI MnBi2Te4. Theoretical modeling captured the initial quenching of a surface-rooted exchange gap within a factor of two but overestimated the bulk demagnetization by one order of magnitude. According to the researchers this mechanism directly explained the sizable gap in the quasi-2D electronic state and the nonzero residual magnetization in even-layer MnBi2Te4 and led to efficient light-induced demagnetization comparable to magnetophotonic crystals, promising an effective manipulation of magnetism and topological orders for future topotronics… read more. Open Access TECHNICAL ARTICLE
Magnetic interactions in a 2D system with itinerant p electrons and localized Mn d electrons. Credit: Science Advances, 9 Aug 2024, Vol 10, Issue 32