期刊
PHYSICAL REVIEW B
卷 106, 期 13, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.106.134413
关键词
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资金
- Estonian Research Council [PRG736]
- Estonian Ministry of Education and Research [IUT23-3]
- European Regional Development Fund [TK134]
- Estonian and Hungarian Academies of Sciences [NMK2018-47]
- Hungarian National Research, Development and Innovation Office-NKFIH Grants [FK 135003]
- Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences
- FWF Austrian Science Fund [I 2816-N27, TAI 334-N]
- Austrian Agency for International Cooperation in Education Research Grant [WTZ HU 08/2020]
- Hungarian NKFIH Grant [2019-2.1.11-TET-2019-00029]
- RIKEN Incentive Research Project
- European Research Council [835279-Catch-22]
We investigated the spin excitations of magnetoelectric LiFePO4 using THz absorption spectroscopy and found magnetic-dipole, electric-dipole active, and magnetoelectric resonances. We used a four-spin mean-field model to reproduce the magnetic field dependence of four low-energy modes. The study also observed additional spin excitations at higher frequencies that were not described by the mean-field model.
We investigated the spin excitations of magnetoelectric LiFePO4 by THz absorption spectroscopy in magnetic fields up to 33 T. By studying their selection rules, we found not only magnetic-dipole, but also electric-dipole active (electromagnons) and magnetoelectric resonances. The magnetic field dependence of four strong low -energy modes is reproduced well by a four-spin mean-field model for fields applied along the three orthorhombic axes. From the fit of magnetization and magnon frequencies, we refined the exchange couplings, single-ion anisotropies, and the Dzyaloshinskii-Moriya interaction parameters. Additional spin excitations not described by the mean-field model are observed at higher frequencies. Some of them show a strong shift with the magnetic field, up to 4 cm-1 T-1, when the field is applied along the easy axis. Based on this field dependence, we attribute these high frequency resonances to the excitation of higher spin multipoles and of two magnons, which become THz-active due to the low symmetry of the magnetically ordered state.
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