Abstract
Neutron diffraction and magnetic susceptibility studies show that orthorhombic single-crystals of topological semimetals Sr(Mn0.9Cu0.1)Sb2 and Sr(Mn0.9Zn0.1)Sb2 undergo three-dimensional C-type antiferromagnetic (AFM) ordering of the Mn2+ moments at TN=200±10 and 210±12 K, respectively, significantly lower than that of the parent SrMnSb2 with TN=297±3 K. Magnetization versus applied magnetic field (perpendicular to MnSb planes) below TN exhibits slightly modified de Haas van Alphen oscillations for the Zn-doped crystal as compared to that of the parent compound. By contrast, the Cu-doped system does not show de Haas van Alphen magnetic oscillations, suggesting that either Cu substitution for Mn changes the electronic structure of the parent compound substantially, or that the Cu sites are strong scatterers of carriers that significantly shorten their mean free path thus diminishing the oscillations. Density functional theory (DFT) calculations including spin-orbit coupling predict the C-type AFM state for the parent, Cu-, and Zn-doped systems and identify the a-axis (i.e., perpendicular to the Mn layer) as the easy magnetization direction in the parent and 12.5% of Cu or Zn substitutions. In contrast, 25% of Cu content changes the easy magnetization to the b-axis (i.e., within the Mn layer). We find that the incorporation of Cu and Zn in SrMnSb2 tunes electronic bands near the Fermi level resulting in different band topology and semimetallicity. The parent and Zn-doped systems have coexistence of electron and hole pockets with opened Dirac cone around the Y-point whereas the Cu-doped system has dominant hole pockets around the Fermi level with a distorted Dirac cone. The tunable electronic structure may point out possibilities of rationalizing the experimentally observed de Haas van Alphen magnetic oscillations.
| Original language | English |
|---|---|
| Article number | 085130 |
| Journal | Physical Review B |
| Volume | 102 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 15 2020 |
| Externally published | Yes |
Funding
This research was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering. Ames Laboratory is operated for the US Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The theoretical capabilities, specific to electronic (band) structure, magnetic order, and magnetic anisotropy predictions, employed in this work were developed in the Critical Materials Institute, an Energy Innovation Hub led by the Ames Laboratory and funded by the U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. R.C. and D.P. would like to acknowledge Ed Moxley for maintaining computational facilities, including the RAMAN cluster and computational software.