Spin-stretching modes in anisotropic magnets: spin-wave excitations in the multiferroic Ba2CoGe2O7

We studied spin excitations in the magnetically ordered phase of the noncentrosymmetric Ba(2)CoGe(2)O(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...

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Vydáno v:Physical review letters Ročník 108; číslo 25; s. 257203
Hlavní autoři: 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
Médium: Journal Article
Jazyk:angličtina
Vydáno: United States 22.06.2012
ISSN:1079-7114, 1079-7114
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Popis
Shrnutí:We studied spin excitations in the magnetically ordered phase of the noncentrosymmetric Ba(2)CoGe(2)O(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.
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ISSN:1079-7114
1079-7114
DOI:10.1103/PhysRevLett.108.257203