A-type antiferromagnetic order in semiconducting EuMg₂Sb₂ single crystals

Journal Article · Mon Jul 18 00:00:00 EDT 2022 · Physical Review. B

DOI:https://doi.org/10.1103/physrevb.106.024418· OSTI ID:1881901

Pakhira, Santanu  ^[1]; Islam, Farhan  ^[1]; O'Leary, Evan  ^[1]; Tanatar, M. A.  ^[1]; Heitmann, Thomas ^[2]; Wang, Lin-Lin  ^[1]; Prozorov, R. ^[1]; Kaminski, Adam ^[1]; Vaknin, David  ^[1]; Johnston, D. C.  ^[1]

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1. Ames Lab., and Iowa State Univ., Ames, IA (United States)
2. Univ. of Missouri, Columbia, MO (United States)

Eu-based Zintl-phase materials EuA₂Pn₂ (A = Mg, In, Cd, Zn; Pn = Bi, Sb, As, P) have generated significant recent interest owing to the complex interplay of magnetism and band topology. Here, we investigated the crystallographic, magnetic, and electronic properties of the layered Zintlphase single crystals of EuMg₂Sb₂ with the trigonal CaAl₂Si₂ crystal structure (space group $$P\bar{3}m1$$). Electrical resistivity measurements complemented with angle-resolved photoemission spectroscopy (ARPES) studies and density functional theory (DFT) calculations find an activated behavior with intrinsic conductivity at high temperatures indicating a semiconducting electronic ground state with a narrow energy gap of 370 meV. Magnetic susceptibility and zero-field heat capacity measurements indicate that the compound undergoes antiferromagnetic (AFM) ordering at the Néel temperature T_N = 8.0(2) K. Here, zero-field neutron-diffraction measurements reveal that the AFM ordering is A-type where the Eu spins (Eu²⁺, S = 7/2) arranged in ab-plane layers are aligned ferromagnetically in the ab plane and the Eu spins in adjacent layers are aligned antiferromagnetically. Eu-moment reorientation within the ab planes in the trigonal AFM domains associated with a very weak inplane magnetic anisotropy is also evident below T_N at low fields < 0.05 T. Although isostructural semimetallic EuMg₂Bi₂ is reported to host Dirac surface states, the observation of narrow-gap semiconducting behavior in EuMg₂Sb₂ implies a strong role of spin-orbit coupling (SOC) in tuning the electronic states of these materials. Our DFT studies also suggest, besides the SOC, the more electronegative and smaller Sb than Bi shifts the low-lying conduction bands along the Γ-A direction to higher energy, resulting in an indirect bulk band gap between the Γ and M points for EuMg₂Sb₂.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1881901
• Report Number(s): IS-J-10,865; TRN: US2307884
• Journal Information: Physical Review. B, Vol. 106, Issue 2; ISSN 2469-9950
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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