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

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.

4 pages, 4 figures, accepted for publication in Phys. Rev. B

References in corpus (3)

• Magnetic inversion symmetry breaking and ferroelectricity in TbMnO3
• Commensurate-Incommensurate Magnetic Phase Transition in Magnetoelectric Single Crystal LiNiPO${}_4$
• Field-induced magnetic phases and electric polarization in LiNiPO4

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