Low-field magnetic anomalies in single crystals of the A-type square-lattice antiferromagnet EuGa4

Journal Article · Wed Jan 25 00:00:00 EST 2023 · Physical Review. B

DOI:https://doi.org/10.1103/physrevb.107.024421· OSTI ID:1922170

Pakhira, Santanu ^[1]; Johnston, D. C. ^[1]

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1. Ames Laboratory, and Iowa State University, Ames, IA (United States)

The body-centered-tetragonal antiferromagnet EuGa₄ was recently identified as a Weyl nodal-line semimetal that exhibits the topological Hall effect below its reported antiferromagnetic (AFM) ordering temperature T_N = 15 – 16.5 K which we find to be T_N = 16.4 ( 2 ) K. The Eu⁺² ions are located at the corners and body centers of the unit cells. EuGa₄ exhibits A-type antiferromagnetic order below T_N, where the Eu²⁺ spin-7/2 moments are ferromagnetically aligned in the ab plane with the Eu moments in adjacent Eu planes along the c axis aligned antiferromagnetically. Low-field magnetization versus field M(H_ab) data at T = 2 K with the field aligned in the ab plane are reported that exhibit anomalous positive curvature up to a critical field H_c1 at which a second-order transition occurs with H_c1 ≈ 0.85 kOe for H∥ [1,1,0] and ≈ 4.8 kOe for H∥[1,0,0]. For larger fields, the linear behavior M_ab = χ(T_N) H a b is followed until the critical field H_c is reached at which all moments become aligned with the applied field. A theory is formulated for T = 0 K that fits the observed M(H_ab) behavior at T = 2 K well, where domains of A -type AFM order with fourfold rotational symmetry occur in the AFM state in zero field. The moments in the four domains reorient to become almost perpendicular to H_ab at H_c1, followed by increasing canting of all moments toward the field with increasing field up to H_c which is reported to be 71 kOe. A first-order transition in M(H_ab) at H_ab = H_c1 is predicted by the theory for T = 0 K when H_ab is at a small angle from the [1,0,0] direction.

• 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: 1922170
• Report Number(s): IS-J 10,988
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 2 Vol. 107; ISSN 2469-9950
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
magnetic anisotropy
magnetic order
magnetic phase transitions
magnetism
methods in magnetism