Controlling magnetic order, magnetic anisotropy, and band topology in the semimetalsSr(Mn0.9Cu0.1)Sb2and

Farhan Islam

¹

,

R. N. P. Choudhary

²

,

Y. Liu

³

et al.

Abstract

Neutron diffraction and magnetic susceptibility studies show that orthorhombic single-crystals of topological semimetals Sr(Mn 0.9 Cu 0.1 )Sb 2 and Sr(Mn 0.9 Zn 0.1 )Sb 2 undergo three-dimensional C-type antiferromagnetic (AFM) ordering of the Mn 2+ moments at T N = 200 ± 10 and 210 ± 12 K, respectively, significantly lower than that of the parent SrMnSb 2 with T N = 297 ± 3 K. Magnetization versus applied magnetic field (perpendicular to MnSb planes) below T N 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 SrMnSb 2 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.

Electronic Structure and Magnetism of Pristine, Defected, and Strained Ti2N MXene

“…The formation of distorted Dirac-like cone apparently diminishes the characteristic of the quantum oscillation as prescribed in Ref. [35]. The formation of Dirac cone (b) just below the Fermi level reveals the idea of n-type self doping character informing the presence of electron carriers even without transforming the electrons from surrounding environment [31].…”

“…5Q). The formation of Dirac cone below the Fermi level reveals the self n-type of doping character, whereas the formation of Dirac cone just above the Fermi level reveals the self p-type doping character indicating the electrons and holes carriers even without transforming the electrons from surrounding environment [31,35]. The origin of gap opening in the Dirac cones are due to hybridization of the electronic wave function between the top and bottom surfaces with the same quantum numbers [71].…”

“…The dispersion of the bands remain linear under the SOC. The non-trivial topological gap with Z 2 = 1 [80,81] form the linear Dirac cones which are responsible for the quantum oscillations [35]. Thus, Ti 2 N is expected as a topological material [82].…”

“…Furthermore, the realization of free-standing single atomic layers of graphene opened a new route towards the topological phenomena in 2D materials [31][32][33][34]. The coexistence of electron and hole pockets with Dirac cone is responsible for quantum oscillation in 3D topological materials beyond the graphene [35]. Similarly, the Zr 2 Si also exhibits anisotropic Dirac cones [36].…”

Unraveling Electronic Structure, Magnetic States, and Topological Phenomena in Pristine, Defected, and Strained Ti2N MXene

“…The non-trivial topological gap with Z 2 = 1 62,63 form the linear Dirac cones which are responsible for the quantum oscillations. 35 Thus, Ti 2 N is expected as a topological material. 64 In the same vein, just above the Fermi level in the region K -Γ, the band inversions are uncovered indicating non-trivial topological features (f and i representations in Figure 5Q), whose characteristic features are already discussed above.…”