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arXiv · 0902.2288

Anomalous spin-waves and the commensurate-incommensurate magnetic phase transition in LiNiPO4

T. B. S. Jensen·N. B. Christensen·M. Kenzelmann·H. M. Rønnow·C. Niedermayer·N. H. Andersen·K. Lefmann·M. Jiménez-Ruiz·F. Demmel·J. Li·J. L. Zarestky·D. Vaknin
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Abstract

Detailed spin-wave spectra of magneto-electric LiNiPO4 have been measured by neutron scattering at low temperatures in the commensurate (C) antiferromagnetic (AF) phase with ordering temperature 20.8 K. An anomalous low-energy mode is observed at the modulation vector of the incommensurate (IC) AF phase appearing above the 20.8 K. A linear spin-wave model based on Heisenberg exchange couplings and single ion anisotropies accounts for all the observed spin-wave dispersions and intensities. Along the b axis an unusually strong next-nearest-neighbor AF coupling competes with the dominant nearest-neighbor AF exchange interaction and causes the IC structure.

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T. B. S. Jensen, N. B. Christensen, M. Kenzelmann, H. M. Rønnow, C. Niedermayer, N. H. Andersen, K. Lefmann, M. Jiménez-Ruiz, F. Demmel, J. Li, J. L. Zarestky, D. Vaknin. 2009-02-13. Anomalous spin-waves and the commensurate-incommensurate magnetic phase transition in LiNiPO4. https://doi.org/10.1103/physrevb.79.092413

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