Magnetic structure and spin-wave dispersion in spinel FeMn<sub>2</sub>O<sub>4</sub>

ORAL

Abstract

Spinel FeMn2O4 is known to exhibit a cation distribution of (Mn2+)A(Mn3+Fe3+)BO4, with Mn2+ mainly occupying the tetrahedral (A) sites forming a diamond lattice, and Fe3+ and Mn3+ sharing the octahedral (B) sites to form a pyrochlore lattice. Powder neutron diffraction reveals a cubic-tetragonal structural transition at ~595 K due to the Jahn-Teller distortion of MnO6 octahedra. A collinear ferrimagnetic order with antiparallel moments between A and B sites is found below ~373 K, and non-collinear ferrimagnetic order appears below ~50 K. Spin wave dispersions in both the collinear and non-collinear ferrimagnetic ordered regions have been determined via inelastic neutron scattering on a large single crystal. At 8 K we observe a spin gap of approximately 5 meV arising from single-ion anisotropy at the orbitally active Mn3+ site. We argue that the orbital degree of freedom of the B-site Mn3+ ion and its coupling to the spin and lattice degrees of freedom play a key role in the structural and magnetic properties in FeMn2O4.

*The work has been supported by the U.S. Department of Energy under EPSCoR Grant No. DESC0012432, with additional support from the Louisiana Board of Regents, and uses sources at a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

–

Presenters

  • Qiang Zhang

    • Department of Physics and Astronomy, Louisiana State Univ - Baton Rouge
    • Department of Physics and Astronomy,, Louisiana State Univ - Baton Rouge

Authors

  • Qiang Zhang

    • Department of Physics and Astronomy, Louisiana State Univ - Baton Rouge
    • Department of Physics and Astronomy,, Louisiana State Univ - Baton Rouge

  • Roshan Nepal

    • Department of Physics & astronomy, Louisiana state University
    • Department of Physics and Astronomy,, Louisiana State Univ - Baton Rouge

  • Wei Tian

    • Oak Ridge National Laboratory
    • Neutron Sciences Directorate, Oak Ridge National Laboratory
    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Masaaki Matsuda

    • Oak Ridge National Lab
    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Quantum Condensed Matter Division, Oak Ridge National Lab
    • Oak Ridge National Laboratory

  • Andrew Christianson

    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory

  • Tao Hong

    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Quantum Condensed Matter Division, Oak Ridge National Laboratory
    • Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Neutron scattering devision, Oak Ridge National Lab

  • John Ditusa

    • Louisiana State Univ - Baton Rouge
    • Physics, Louisiana State Univ
    • Department of Physics and Astronomy, Louisiana State Univ - Baton Rouge
    • Department of Physics and Astronomy,, Louisiana State Univ - Baton Rouge

  • Stephen Nagler

    • Quantum Condensed Matter Division, Oak Ridge National Laboratory
    • Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Neutron Scattering Division, Oak Ridge National Laboratory

  • Rongying Jin

    • Department of Physics and Astronomy, Louisiana State University
    • Physics and Astronomy, Louisiana State Univ - Baton Rouge
    • Department of Physcis and Astronomy, Louisiana State University
    • Department of Physics & astronomy, Louisiana state University
    • Department of Physics, Louisiana State University
    • Louisiana State Univ - Baton Rouge
    • Physics and Astronomy, Louisiana State University
    • Physics, Louisiana State Univ
    • Department of Physics and Astronomy,, Louisiana State Univ - Baton Rouge