TY - JOUR
T1 - Electronic structure and lattice dynamics of Li2Ni(WO4)2
AU - Chung, Yun Chen
AU - Karna, Sunil K.
AU - Chou, Fan Cheng
AU - Liu, Hsiang Lin
N1 - Publisher Copyright:
© 2019 The Physical Society of the Republic of China (Taiwan)
PY - 2019/8
Y1 - 2019/8
N2 - 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.
AB - 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.
KW - Optical spectroscopy
KW - Spin-phonon coupling
KW - Strongly correlated electron system
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U2 - 10.1016/j.cjph.2019.05.027
DO - 10.1016/j.cjph.2019.05.027
M3 - Article
AN - SCOPUS:85067432736
SN - 0577-9073
VL - 60
SP - 473
EP - 480
JO - Chinese Journal of Physics
JF - Chinese Journal of Physics
ER -