Electronic structure and lattice dynamics of Li2Ni(WO4)2 |
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| Affiliation: | 1. Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan;2. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan;1. Center for Health Promotion, Samsung Medical Center, Seoul, Korea;2. Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea;3. Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea;4. Statistics and Data Center, Research Institute for Future Medicine, Samsung Medical Center, Seoul, Korea;5. Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea;1. Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea;2. Department of Materials Science and Engineering, Hanyang University, Seoul 04763, Republic of Korea;3. Department of Materials and Metallurgical Engineering, Kangwon National University, Samcheok 25913, Republic of Korea;4. Agency for Defense Development, Daejeon 34186, Republic of Korea |
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| Abstract: | We combined spectroscopic ellipsometry and Raman scattering measurements to explore the electronic structure and lattice dynamics in Li2Ni(WO4)2. The optical absorption spectrum of Li2Ni(WO4)2 measured at room temperature presents a direct optical band gap at 2.25 eV and two bands near 5.2 and 6.0 eV, which are attributed to charge-transfer transitions from oxygen 2p states to nickel 3d or tungsten 5p states. The Raman scattering spectrum of Li2Ni(WO4)2 measured at room temperature presents seventeen phonon modes at approximately 112, 143, 193, 222, 267, 283, 312, 352, 387, 418, 451, 476, 554, 617, 754, 792, and 914 cm−1. When the temperature is decreased to 20 K, the frequency, linewidth, and normalized intensity of all phonon modes exhibited almost no temperature dependence. Upon cooling across 13 K, which is the antiferromagnetic phase transition temperature, the oxygen octahedra stretching mode at 914 cm−1 exhibited a softening and an increase in intensity, thus suggesting a coupling between the magnetic and lattice degrees of freedom. The spin-phonon coupling constant was estimated to be 0.94 mRy/Å2, indicating a weak spin-phonon interaction in Li2Ni(WO4)2. |
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