Terahertz study of potential multiferroic materials Sr$_2$FeSi$_2$O$_7$ and BaFe$_{12}$O$_{19}$

ORAL

Abstract

We present data on the complex dielectric function of two iron-based quantum magnets in the terahertz frequency range. We study the phase transitions in Sr$_2$FeSi$_2$O$_7$ at low temperature when it becomes a collinear antiferromagnet, in contrast with the canted antiferromagnetic state of iso-structural multiferroic Ba$_2$CoGe$_2$O$_7$. We compare the terahertz response of these two materials in light of the recent observation of electromagnon excitations in Ba$_2$CoGe$_2$O$_7$. We have also studied BaFe$_{12}$O$_{19}$, a hexagonal ferromagnet that is predicted to have an antiferroelectric state. We will report experiments at terahertz frequencies probing this predicted state.

*Work partially supported by the NSF MRSEC Center for Emergent Materials under grant DMR-1420451.

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Authors

  • Thuc T. Mai

    • Center for Emergent Materials, Department of Physics. The Ohio State University. Columbus, OH 43210

  • M.T. Warren

    • Center for Emergent Materials, Department of Physics. The Ohio State University. Columbus, OH 43210

  • J. Brangham

    • Center for Emergent Materials, Department of Physics. The Ohio State University. Columbus, OH 43210

  • T-H. Hwan

    • POSTECH, South Korea

  • S-W. Cheong

    • Department of Physics, Rutgers University

  • J. Yan

    • Oak Ridge National Laboratory and University of Tennessee Knoxville

  • R. Vald\'es Aguilar

    • Center for Emergent Materials, Department of Physics. The Ohio State University. Columbus, OH 43210