Relationship between Antisite Defects, Magnetism, and Band Topology in MnSb₂Te₄ Crystals with T_C ≈ 40 K

Abstract

MnSb2Te4 has attracted extensive attention because of its rich and adjustable magnetic properties. Here, using a modified crystal growth method, ferrimagnetic MnSb2Te4 crystals with enhanced Curie temperature (T C) of about 40 K with dominant hole-type carriers and intrinsic anomalous Hall effect is obtained. Time- and angle-resolved photoemission spectroscopy reveals that surface states are absent in both antiferromagnetic and ferrimagnetic MnSb2Te4, implying that they have topologically trivial electronic structures. We propose that the enhancement of ferrimagnetism mainly originates from the increase of intralayer magnetic coupling caused by the decrease of Sb content at Mn sites when the decrease of Mn concentration at Sb sites would prefer the nontrival band topology. Moreover, it is known that the initial saturation moment (M is) is sensitive to the concentrations of Mn/Sb antisite defects; thus, the M is could be a valuable parameter to evaluate the magnetic and topological properties of MnX2n Te3n+1 (X = Bi, Sb) families.

Antisite-Defects Control of Magnetic Properties in MnSb2Te4

“…Due to Δ S mix , the compounds with Mn–Sb site mixing can be thermodynamically stabilized. Consequently, Mn–Sb antisite defects were commonly observed in MST, regardless of the growth method employed, including the solid-state reaction route, flux-growth method, chemical vapor transport method, and molecular beam epitaxy method. ,,,,,− ,,,− The Mn–Sb defects can be further controlled by the growth kinetics.…”

“…As the Mn Bi concentration is small, MBT still exhibits an overall A-type AFM ground state (i.e., the interlayer AFM interactions are dominant). In MST, due to similar ionic radii of Sb 3+ and Mn 2+ (smaller than that of Bi 3+ ), a higher Mn–Sb antisite concentration (around 15% Mn Sb and 30% Sb Mn ) is reported when compared to the Mn–Bi antisite concentration (around 5% Mn Bi and 20% Bi Mn ) in MBT. ,,,− Therefore, as introduced above, these antisite defects exert significant influences on the overall magnetic structures (AFM or FIM) and transition temperatures of MST. ,,− In addition to magnetism, the Mn–Bi/Sb antisite defects would also induce electron/hole doping and alter the Fermi surface, band inversion, and topology of Mn­(Sb/Bi) 2 n +2 Te 3 n +4 . − Despite the importance of the defects, their formation mechanism, the methods to tune their concentration and distribution, and how they can control the magnetism remain unclear.…”

“…22 Experimentally, by angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS) measurements, AFM MST was shown to be topologically trivial, 24 and FM MST was shown to be either topologically trivial or topologically nontrivial. 19,24 The inconsistent results were partially ascribed to the presence of a considerable number of defects in the prepared samples. Therefore, investigation of defects in Mn(Sb/Bi) 2n+2 Te 3n+4 is of great importance.…”

“…Theoretically, AFM MST has been proposed to be either an AFM topological insulator or a topologically trivial material, − and FM MST was predicted to be a Weyl semimetal by calculations . Experimentally, by angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS) measurements, AFM MST was shown to be topologically trivial, and FM MST was shown to be either topologically trivial or topologically nontrivial. , The inconsistent results were partially ascribed to the presence of a considerable number of defects in the prepared samples. Therefore, investigation of defects in Mn­(Sb/Bi) 2 n +2 Te 3 n +4 is of great importance.…”

Fermiology of Chiral Cadmium Diarsenide CdAs2, a Candidate for Hosting Kramers–Weyl Fermions

“…Crystal symmetries play a pivotal role in determining the electronic properties of various quantum systems, and their study has garnered substantial interest for both fundamental research and technological applications. − Crystals exhibiting well-defined handedness, due to the breaking of inversion, mirror, or any other roto-inversion symmetries, are referred to as chiral crystals. − Even in their nonmagnetic state, these chiral crystals show universal topological electronic properties due to their spin–orbit coupling and crystalline chirality, resulting in the presence of Kramers–Weyl Fermions in their spectrum. , These Fermions are pinned to Kramers degenerate points, leading to the appearance of topological gaps, which are significantly larger than those observed in Weyl semimetals . Within such gaps, ubiquitous topological properties, such as quantized chiral charges, negative longitudinal magnetoresistance, and nontrivial Chern numbers can arise, opening up exciting avenues for engineering exotic transport phenomena and applications.…”