Abstract
Eu5In2Sb6 is an orthorhombic nonsymmorphic 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 and belongs to a family of Zintl materials that may host an axion insulator. Using single crystal neutron diffraction, we show that the TN1=14K 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=7K that doubles the unit cell along the c axis (k2=(0012)). 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 b and a axis, respectively. As the k2 component develops, the amplitude of the k1 component is reduced, which indicates a 2k noncollinear 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.
Original language | English |
---|---|
Article number | 014432 |
Journal | Physical Review B |
Volume | 109 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1 2024 |
Funding
V.C.M. thanks N. Peter Armitage for helpful discussions. This research was conducted at the Institute for Quantum Matter, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science, Basic Energy Sciences, under Award No. DE-SC0019331. This work is based on neutron experiments performed at the NIST Center for Neutron Research. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The MPMS was funded by the National Science Foundation, Division of Materials Research, Major Research Instrumentation Program, under Award No. 1828490. C.L.B. and V.C.M. were supported by the Gordon and Betty Moore foundation EPIQS program under Grant No. GBMF9456.