Magnetic structure and spin-wave dispersion in spinel FeMn2O4

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.

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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