2023, Tcakaev, Abdul‐Vakhab, Rubrecht, Bastian, Facio, Jorge I., Zabolotnyy, Volodymyr B., Corredor, Laura T., Folkers, Laura C., Kochetkova, Ekaterina, Peixoto, Thiago R. F., Kagerer, Philipp, Heinze, Simon, Bentmann, Hendrik, Green, Robert J., Gargiani, Pierluigi, Valvidares, Manuel, Weschke, Eugen, Haverkort, Maurits W., Reinert, Friedrich, van den Brink, Jeroen, Büchner, Bernd, Wolter, Anja U. B., Isaeva, Anna, Hinkov, Vladimir

The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi2Te4 and MnBi4Te7 benchmark the (MnBi2Te4)(Bi2Te3)n family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi2Te4 septuple layers (SLs). However, the QAHE realization is complicated in MnBi2Te4 and MnBi4Te7 due to the substantial antiferromagnetic (AFM) coupling between the SLs. An FM state, advantageous for the QAHE, can be stabilized by interlacing the SLs with an increasing number n of Bi2Te3 quintuple layers (QLs). However, the mechanisms driving the FM state and the number of necessary QLs are not understood, and the surface magnetism remains obscure. Here, robust FM properties in MnBi6Te10 (n = 2) with Tc ≈ 12 K are demonstrated and their origin is established in the Mn/Bi intermixing phenomenon by a combined experimental and theoretical study. The measurements reveal a magnetically intact surface with a large magnetic moment, and with FM properties similar to the bulk. This investigation thus consolidates the MnBi6Te10 system as perspective for the QAHE at elevated temperatures.

2015, Tominaga, Junji, Kolobov, Alexander V., Fons, Paul J., Wang, Xiaomin, Saito, Yuta, Nakano, Takashi, Hase, Muneaki, Murakami, Shuichi, Herfort, Jens, Takagaki, Yukihiko

Multiferroics, materials in which both magnetic and electric fields can induce each other, resulting in a magnetoelectric response, have been attracting increasing attention, although the induced magnetic susceptibility and dielectric constant are usually small and have typically been reported for low temperatures. The magnetoelectric response usually depends on d-electrons of transition metals. Here we report that in [(GeTe)2(Sb2Te3)l]m superlattice films (where l and m are integers) with topological phase transition, strong magnetoelectric response may be induced at temperatures above room temperature when the external fields are applied normal to the film surface. By ab initio computer simulations, it is revealed that the multiferroic properties are induced due to the breaking of spatial inversion symmetry when the p-electrons of Ge atoms change their bonding geometry from octahedral to tetrahedral. Finally, we demonstrate the existence in such structures of spin memory, which paves the way for a future hybrid device combining nonvolatile phase-change memory and magnetic spin memory.