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  Golias, E.; Weschke, E.; Flanagan, T.; Schierle, E.; Richardella, A.; Rienks, E. D. L.; Mandal, P. S.; Varykhalov, A.; Sánchez-Barriga, J.; Radu, F.; Samarth, N.; Rader, O.: Magnetization relaxation and search for the magnetic gap in bulk-insulating V-doped (Bi,Sb)₂Te₃. Applied Physics Letters 119 (2021), p. 132404/1-6

10.1063/5.0070557
Open Access Version

Abstract:
V-doped (Bi,Sb)2Te3 has a ten times higher magnetic coercivity than its Cr-doped counterpart and, therefore, is believed to be advantageous for the quantum anomalous Hall effect (QAHE). The QAHE requires the opening of a magnetic bandgap at the Dirac point. We do not find this gap by angle-resolved photoelectron spectroscopy down to 1 K. By x-ray magnetic circular dichroism (XMCD), we directly probe the magnetism at the V site and derive spin and orbital magnetic moments of 1.69 and –0.22 μB/atom. Hysteresis curves of the XMCD signal show a strong dependence of the coercivity on the ramping velocity of the magnetic field. The XMCD signal decays on a timescale of minutes, which we conclude contributes to the absence of a detectable magnetic gap at the Dirac point.