Sketch of the ideal crystal structure of epitaxial MnSb2Te4 as side view and top view (as shown in figure 1 of the publication).
In a coordinated work with Gunther Springholz (Johannes Kepler University, Austria) and Oliver Rader (Helmholtz Zentrum Berlin for Materials and Energy), ML4Q member Markus Morgenstern at RWTH Aachen published the results of recent work on ferromagnetic topological insulators in Advanced Materials. In their work, the authors show p-type MnSb2Te4, previously considered topologically trivial, to be a ferromagnetic topological insulator for a few percent Mn excess.
Quantum effects are most noticeable at extremely low temperatures, which limits their usefulness for technical applications. Thin films of MnSb2Te4, however, which tend to have a small excess of manganese provide spectacular properties: The material proves to be a topological insulator and is ferromagnetic up to comparatively high temperatures of 50 Kelvin. This makes this class of materials suitable for quantum bits, but also for spintronics in general or applications in high-precision metrology.
In this study, two particularly important physical properties in thin films of MnSb2Te4 are described: Such structures are robust topological insulators and also ferromagnetic up to nearly 50 Kelvin. “According to the theoretical considerations published so far, the material should be neither ferromagnetic nor topological,” says Oliver Rader. “However, we have now experimentally demonstrated exactly these two properties.” Apparently, the theory assumed an ideally ordered structure, but the authors see that additional manganese atoms have led to some disorder which explains the difference in the observed material properties.
The properties are exceptionally robust, occurring up to a temperature of just under 50 K, which is three times higher than the best ferromagnetic systems known. This makes this material an interesting candidate for spintronics and even qubits.
[based on the press release of the HZB for Materials and Energy]
Publication:
Mn-Rich MnSb2Te4: A Topological Insulator with Magnetic Gap Closing at High Curie Temperatures of 45–50 K
Stefan Wimmer, Jaime Sánchez-Barriga, Philipp Küppers, Andreas Ney, Enrico Schierle, Friedrich Freyse, Ondrej Caha, Jan Michalička, Marcus Liebmann, Daniel Primetzhofer, Martin Hoffman, Arthur Ernst, Mikhail M. Otrokov, Gustav Bihlmayer, Eugen Weschke, Bella Lake, Evgueni V. Chulkov, Markus Morgenstern, Günther Bauer, Gunther Springholz and Oliver Rader
Advanced Materials (published online 1 September 2021), DOI: https://doi.org/10.1002/adma.202102935
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