Spin-stretching modes in anisotropic magnets: Spin-wave excitations in the multiferroic Ba 2CoGe 2O 7

K. Penc, J. Romhányi, T. Rõõm, U. Nagel, A. Antal, T. Fehér, A. Jánossy, H. Engelkamp, H. Murakawa, Y. Tokura, D. Szaller, S. Bordács, I. Kézsmárki

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38 Citations (Scopus)

Abstract

We studied spin excitations in the magnetically ordered phase of the noncentrosymmetric Ba 2CoGe 2O 7 in high magnetic fields up to 33 T. In the electron spin resonance and far infrared absorption spectra we found several spin excitations beyond the two conventional magnon modes expected for such a two-sublattice antiferromagnet. We show that a multiboson spin-wave theory describes these unconventional modes, including spin-stretching modes, characterized by an oscillating magnetic dipole and quadrupole moment. The lack of inversion symmetry allows each mode to become electric dipole active. We expect that the spin-stretching modes can be generally observed in inelastic neutron scattering and light absorption experiments in a broad class of ordered S>1/2 spin systems with strong single-ion anisotropy and/or noncentrosymmetric lattice structure.

Original languageEnglish
Article number257203
JournalPhysical review letters
Volume108
Issue number25
DOIs
Publication statusPublished - Jun 19 2012

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Penc, K., Romhányi, J., Rõõm, T., Nagel, U., Antal, A., Fehér, T., Jánossy, A., Engelkamp, H., Murakawa, H., Tokura, Y., Szaller, D., Bordács, S., & Kézsmárki, I. (2012). Spin-stretching modes in anisotropic magnets: Spin-wave excitations in the multiferroic Ba 2CoGe 2O 7. Physical review letters, 108(25), [257203]. https://doi.org/10.1103/PhysRevLett.108.257203