Magnetic and electronic structure of Dirac semimetal candidate EuMnSb2

Abstract

We report an experimental study of the magnetic order and electronic structure and transport of the layered pnictide EuMnSb2, performed using neutron diffraction, angle-resolved photoemission spectroscopy (ARPES), and magnetotransport measurements. We find that the Eu and Mn sublattices display antiferromagnetic (AFM) order below T Eu N = 21(1) K and T Mn N = 350(2) K respectively. The former can be described by an A-type AFM structure with the Eu spins aligned along the c axis (an in-plane direction), whereas the latter has a C-type AFM structure with Mn moments along the a-axis (perpendicular to the layers). The ARPES spectra reveal Dirac-like linearly dispersing bands near the Fermi energy. Furthermore, our magnetotransport measurements show strongly anisotropic magnetoresistance, and indicate that the Eu sublattice is intimately coupled to conduction electron states near the Dirac point. 75.30.Gw, 74.70.Xa Topological semimetals can host quasiparticle excitations which masquerade as massless fermions due to the linearly-dispersing electronic bands created by interactions with the crystal lattice. The Dirac or Weyl nodes, where the conduction and valence bands meet in momentum space, are robust against small perturbations due to the protection afforded by crystalline symmetries or the topology of the electronic bands 1-5 . Topological semimetals exhibit exceptional electronic transport properties (e.g. extremely high carrier mobility and large linear magnetoresistance) and the control of these exotic charge carriers could help realize a new generation of spintronic devices with low power consumption 6-8 .Such control can potentially be realized in materials in which magnetic order coexists with non-trivial electronic band topology. Recent ARPES, quantum oscillation, neutron diffraction and ab initio band structure studies suggest that materials in the AMnSb 2 (A = Ca, Sr, Ba, Eu, Yb) family display many of the required properties 9-18 . The two-dimensional zig-zag layer of Sb atoms [ Fig. 1] in these 112-pnictides play host to fermions which can be described by the relativistic Dirac or Weyl equations. Furthermore, the electronic transport in this family of materials also displays large magnetoresistive effects, suggesting a coupling between the magnetism and charge carriers 9-17 . These effects could be driven by changes in the electronic band structure topology due to changes in the symmetry of the spin structures induced by the applied field 19 .Within the AMnSb 2 family, EuMnSb 2 is of particular interest because the conducting zig-zag layer of Sb atoms is sandwiched between two interpenetrating magnetic sublattices (Eu and Mn), as shown in Fig. 1(a). Such a structure may lead to an enhancement of the coupling between the topological quasiparticles and mag-netism, compared to that in compounds with a nonmagnetic atom on the A site. The dramatic magnetoresistive behaviour observed in a recent work 20 is evidence for the importance of this coupling. Up to now, however, the nature of the magnetic order in...

Zero-field magnetic ground state of EuMg2Bi2

“…Recent studies of rare-earth-based metallic systems have revealed novel electronic states arising from a complex interplay of magnetism and electron-band topology [1][2][3][4][5][6][7]. EuMg 2 Bi 2 is one such system that undergoes antiferromagnetic (AFM) ordering below a Néel temperature T N ≈ 6.7 K [8][9][10] and is also reported to host multiple Dirac points located at different energies with respect to the Fermi energy [10].…”

Toward Controllable Quantum Transports and Novel Magnetic States in Eu1–xSrxMnSb2

“…Interestingly, EuMnSb 2 exhibits distinct properties from EuMnBi 2 and conflicting results have been reported [16][17][18] . The magneto-transport properties reported by Yi et al 16 are not indicative of a Dirac semimetallic state, while Soh et al 17 observed linear band dispersion near the Fermi level in the ARPES measurements of EuMnSb 2 and claimed it may be a Dirac semimetal.…”

“…A large family of ternary AMnCh 2 "112" compounds (A =alkali earth/rare earth elements, Ch = Bi or Sb) 6,7,[13][14][15] are particularly interesting since a few of them have been reported to be magnetic Dirac semimetals where the Bi or Sb layers host relativistic fermions. AMnCh 2 (A=Ce, Pr, Nd, Eu, Sm; C=Bi or Sb) [15][16][17] possesses two magnetic sub-lattices, formed by the magnetic moments of rare-earth A and Mn respectively, in contrast with other compounds showing only Mn magnetic lattice in this family. The conducting Bi/Sb layers and the insulating magnetic Mn-Bi(Sb)…”

“…Moreover, the magnetic structure of EuMnSb 2 is also thought to be distinct from that of EuMnBi 2 , with controversial reports on Eu and Mn moments being perpendicular 17 or canted to each other 18 .…”

A new topological semimetal candidate: SmMnBi2

“…Many types of materials have emerged as Dirac or Weyl semimetal candidates, and one such family of materials is MMnX 2 (M = alkaline earth/rare earth metals, X = Sb/Bi) (Park et al, 2011;Wang, Graf et al, 2011;Wang et al, 2012;Lee et al, 2013;Farhan et al, 2014;May et al, 2014;Liu et al, 2016;Chinotti et al, 2016;Huang et al, 2017;Borisenko et al, 2019;Soh, Manuel et al, 2019;Soh, Jacobsen et al, 2019;Pal et al, 2019;Gong et al, 2020). They have been established as Dirac semimetals, with one member, YbMnBi 2 , emerging as a Weyl semimetal (Borisenko et al, 2019).…”