Enhancing Magnetic Ordering in Cr-Doped Bi[subscript 2]Se[subscript 3] Using High-T[subscript C] Ferrimagnetic Insulator

Abstract

We report a study of enhancing the magnetic ordering in a model magnetically doped topological insulator (TI), Bi[subscript 2–x]Cr[subscript x]Se[subscript 3], via the proximity effect using a high-T[subscript C] ferrimagnetic insulator Y[subscript 3]Fe[subscript 5]O[subscript 12]. The FMI provides the TI with a source of exchange interaction yet without removing the nontrivial surface state. By performing the elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally observed an enhanced T[subscript C] of 50 K in this magnetically doped TI/FMI heterostructure. We have also found a larger (6.6 nm at 30 K) but faster decreasing (by 80% from 30 to 50 K) penetration depth compared to that of diluted ferromagnetic semiconductors (DMSs), which could indicate a novel mechanism for the interaction between FMIs and the nontrivial TIs surface.