Evidence for ferromagnetic coupling at the doped topological insulator/ferrimagnetic insulator interface

Abstract

One of the major obstacles of the magnetic topological insulators (TIs) impeding their practical use is the low Curie temperature (T-c). Very recently, we have demonstrated the enhancement of the magnetic ordering in Cr-doped Bi2Se3 by means of proximity to the high-T-c ferrimagnetic insulator (FMI) Y3Fe5O12 and found a large and rapidly decreasing penetration depth of the proximity effect, suggestive of a different carrier propagation process near the TI surface. Here we further present a study of the interfacial magnetic interaction of this TI/FMI heterostrucutre. The synchrotron-based X-ray magnetic circular dichroism (XMCD) technique was used to probe the nature of the exchange coupling of the Bi2-xCrxSe3/Y3Fe5O12 interface. We found that the Bi2-xCrxSe3 grown on Y3Fe5O12(111) predominately contains Cr3+ cations, and the spin direction of the Cr3+ is aligned parallel to that of tetrahedral Fe3+ of the YIG, revealing a ferromagnetic exchange coupling between the Bi2-xCrxSe3 and the Y3Fe5O12. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.