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  Prokes, K.; Luo, C.; Ryll, H.; Schierle, E.; Marchenko, D.; Weschke, E.; Radu, F.; Abrudan, R.; Volobuev, V.V.; Springholz, G.; Rader, O.: Search for enhanced magnetism at the interface between Bi₂Se₃ and EuSe. Physical Review B 103 (2021), p. 115438/1-8

10.1103/physrevb.103.115438
Open Accesn Version

Abstract:
Enhanced magnetism has recently been reported for the topological-insulator/ferromagnet interface Bi2Se3/EuS with Curie temperatures claimed to be raised above room temperature from the bulk EuS value of 16 K. Here we investigate the analogous interface Bi2Se3/EuSe. EuSe is a low-temperature layered ferrimagnet that is particularly sensitive to external perturbations. We find that superconducting quantum interference device (SQUID) magnetometry of Bi2Se3/EuSe heterostructures reveals precisely the magnetic phase diagram known from EuSe, including the ferrimagnetic phase below 5 K, without any apparent changes from the bulk behavior. Choosing a temperature of 10 K to search for magnetic enhancement, we determine an upper limit for a possible magnetic coercive field of 3 mT. Using interface sensitive x-ray absorption spectroscopy we verify the magnetic divalent configuration of the Eu at the interface without contamination by Eu3+, and by x-ray magnetic circular dichroism (XMCD) we confirm at the interface the magnetic hysteresis obtained by SQUID. XMCD data obtained at 10 K in a magnetic field of 6 T indicate a magnetic spin moment of mz,spin=7μB/Eu2+, in good agreement with the SQUID data and the expected theoretical moment of Eu2+. Subsequent XMCD measurements in zero field show, however, that sizable remanent magnetization is absent at the interface for temperatures down to about 10 K.