Magnetic and Electronic Properties of Gd-Doped Topological Insulator Bi 1.09 Gd 0.06 Sb 0.85 Te 3
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, DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Magnetic and Electronic Properties of Gd-Doped Topological Insulator Bi1.09Gd0.06Sb0.85Te3 S. O. Filnova,*, Yu. A. Surnina, A. V. Korolevaa, I. I. Klimovskikha, D. A. Estyunina, A. Yu. Varykhalovb, K. A. Bokaia, K. A. Kokha,c,d, O. E. Tereshchenkoa,c,e, V. A. Golyashova,c,e, E. V. Shevchenkoa, and A. M. Shikina a St.
Petersburg State University, St. Petersburg, 198504 Russia Helmholtz-Zentrum Berlin fur Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany c Novosibirsk State University, Novosibirsk, 630090 Russia d Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia e Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected] b
Received February 5, 2019; revised March 25, 2019; accepted April 9, 2019
Abstract—The recent realization of quantum anomalous Hall effect and Majorana fermions observation enhance interest in magnetism investigation in topological insulators. In this work, the electronic and magnetic structure of the Gd-doped topological insulator Bi1.09Gd0.06Sb0.85Te3 were systematically studied by means of angle-resolved photoemission spectroscopy, resonance photoemission spectroscopy (ResPES) and SQUID magnetometry. Resonant features related to the Gd density of states near the Fermi level are experimentally observed. Study of magnetic structure showed antiferromagnetic ordered bulk at low temperatures as well as presence of hysteresis loop at elevated temperatures. Finally, possible mechanism of magnetism and its relation to observed electronic features are discussed. DOI: 10.1134/S106377611908003X
1. INTRODUCTION Topological insulators (TIs) are materials with a bulk band gap and topologically protected conductive surface states with a linear dispersion E(k||) forming the Dirac cone. Such states are spin-polarized, formed due to the strong spin-orbit interaction and localized in the bulk band gap [1, 2]. An intriguing feature of topological surface states is their protection from the backscattering determined by the requirements of the time reversal symmetry (TRS) [3, 4]. This leads to a possibility of the Dirac cone preserving even in the presence of external electric field [5, 6], nonmagnetic impurities [7, 8] or after thin film formation atop the TIs surface [9, 10]. Moreover, topological surface states may be stable even after annealing [11] and surface degradation. [12] The most well-known TIs at the moment are binary or triple compounds based on Bi(Sb) and Te(Se) [13–16]. An important step in understanding the properties of TIs is based on changing their electronic structure when the TRS is broken. For example, TRS may be broken by doping of magnetic atoms. Magnetic field breaks the TRS lifting the Kramers degeneracy between up and down spins and can open a local gap at the Dirac point [17]. A subsequent study of TIs
doped by magnetic a
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