Noncollinear 2k Antiferromagnetism in the Zintl Semiconductor Eu5In2Sb6

Published

January 29, 2024

Author(s)

Vincent Morano, Jonathan N. Gaudet, Nicodemos Varnava, Tanya Berry, Thomas Halloran, Chris Lygouras, Xiaoping Wang, Christina M. Hoffman, Guangyong Xu, Jeffrey Lynn, Tyrel McQueen, David Vanderbilt, Collin L. Broholm

Abstract

Eu5In2Sb6 is an orthorhombic non-symmorphic small band gap semiconductor with three distinct Eu2+ sites and two low-temperature magnetic phase transitions. The material displays one of the greatest (negative) magnetoresistances of known stoichiometric antiferromagnets [1] and belongs to a family of Zintl materials that may host an axion insulator [2]. Using single crystal neutron diffraction, we show that the TN1 = 14 K second-order phase transition is associated with long-range antiferromagnetic order within the chemical unit cell (k1 = (000)). Upon cooling below TN1, the relative sublattice magnetizations of this structure vary until a second-order phase transition at TN2 = 7 K that doubles the unit cell along the cˆ axis (K2 = (001/2)). We show the anisotropic susceptibility and our magnetic neutron diffraction data are consistent with magnetic structures described by the Γ3 irreducible representation with the staggered magnetization of the k1 and k2 components polarized along the ˆb and aˆ axis, respectively. As the k2 component develops, the amplitude of the k1 component is reduced, which indicates a 2k non-collinear magnetic structure. Density functional theory is used to calculate the energies of these magnetic structures and to show the k1 phase is a metal so TN1 is a rare example of a unit-cell-preserving second-order phase transition from a paramagnetic semiconductor to an antiferromagnetic metal. DFT indicates the transition at TN2 to a doubled unit cell reduces the carrier density of the metal, which is consistent with resistivity data [1]. We show the anisotropic susceptibility and our magnetic neutron diffraction data are consistent with magnetic structures described by the Γ3 irreducible representation with the staggered magnetization of the k1 and k2 components polarized along the ˆb and aˆ axis, respectively. As the k2 component develops, the amplitude of the k1 component is reduced, which indicates a 2k non-collinear magnetic structure. Density functional theory is used to calculate the energies of these magnetic structures and to show the k1 phase is a metal so TN1 is a rare example of a unit-cell-preserving second-order phase transition from a paramagnetic semiconductor to an antiferromagnetic metal. DFT indicates the transition at TN2 to a doubled unit cell reduces the carrier density of the metal, which is consistent with resistivity data [1].

Citation

Physical Review B

Volume

109

Issue

1

Pub Type

Journals

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https://doi.org/10.1103/PhysRevB.109.014432

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Keywords

Magnetic Order, Zintl semiconductor, Neutron Diffraction, noncollinear moments, nonsymmorphic structure, two wavevector antiferromagnetism

Citation

Morano, V. , Gaudet, J. , Varnava, N. , Berry, T. , Halloran, T. , Lygouras, C. , Wang, X. , Hoffman, C. , Xu, G. , Lynn, J. , McQueen, T. , Vanderbilt, D. and Broholm, C. (2024), Noncollinear 2k Antiferromagnetism in the Zintl Semiconductor Eu5In2Sb6, Physical Review B, [online], https://doi.org/10.1103/PhysRevB.109.014432, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956987 (Accessed December 12, 2024)