中国物理B ›› 2006, Vol. 15 ›› Issue (5): 1090-1095.doi: 10.1088/1009-1963/15/5/038

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Infrared active phonon modes and ionicity of single crystal MgAl2O4

姚端正1, 毕聪志2, 马继云3, 颜俊3, 方煦3, 赵柏儒3, 邱祥冈3   

  1. (1)Department of Physics, Wuhan University, Wuhan 430072, China; (2)Department of Physics, Wuhan University, Wuhan 430072, China;National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China; (3)National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
  • 收稿日期:2005-11-21 修回日期:2006-03-03 出版日期:2006-05-20 发布日期:2006-05-20
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No 10474128) and Chinese Academy of Sciences.

Infrared active phonon modes and ionicity of single crystal MgAl2O4

Bi Cong-Zhi (毕聪志)ab, Ma Ji-Yun (马继云)b, Yan Jun (颜俊)b, Fang Xu (方煦)b, Zhao Bai-Ru (赵柏儒)b, Yao Duan-Zheng (姚端正)a, Qiu Xiang-Gang(邱祥冈)b   

  1. a Department of Physics, Wuhan University, Wuhan 430072, China; b National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
  • Received:2005-11-21 Revised:2006-03-03 Online:2006-05-20 Published:2006-05-20
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No 10474128) and Chinese Academy of Sciences.

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摘要： Near-normal incident infrared reflectivity spectra of (100) MgAl2O4 spinel single crystal have been measured at different temperatures in the frequency region between 50 and 6000cm-1. Eight infrared-active phonon modes are identified, which are fitted with the factorized form of the dielectric function. The dielectric property and optical conductivity of the MgAl2O4 crystal are analysed. From TO/LO splitting, the effective Szigeti charges and Born effective charges at different temperatures are calculated for studying the ionicity and the effect of polarization. Based on the relationship between the (LO--TO)1 splitting, which represents the transverse and longitudinal frequencies splitting of the highest energy phonon band in the reflectivity spectrum, and the ionic-covalent parameter, the four main phonon modes are assigned. MgAl2O4can be considered as a pure ionic crystal and its optical characters do not change with decreasing temperature, so it may be used as a suitable substrate for high-Tc superconducting thin films.

关键词: MgAl2O4 single crystal, phonon, dielectric function, effective charges

Abstract: Near-normal incident infrared reflectivity spectra of (100) MgAl2O4 spinel single crystal have been measured at different temperatures in the frequency region between 50 and 6000cm-1. Eight infrared-active phonon modes are identified, which are fitted with the factorized form of the dielectric function. The dielectric property and optical conductivity of the MgAl2O4 crystal are analysed. From TO/LO splitting, the effective Szigeti charges and Born effective charges at different temperatures are calculated for studying the ionicity and the effect of polarization. Based on the relationship between the (LO--TO)1 splitting, which represents the transverse and longitudinal frequencies splitting of the highest energy phonon band in the reflectivity spectrum, and the ionic-covalent parameter, the four main phonon modes are assigned. MgAl2O4can be considered as a pure ionic crystal and its optical characters do not change with decreasing temperature, so it may be used as a suitable substrate for high-Tc superconducting thin films.

Key words: MgAl2O4 single crystal, phonon, dielectric function, effective charges

中图分类号:  (Other nonmetallic inorganics)

  • 78.30.Hv
63.20.D- (Phonon states and bands, normal modes, and phonon dispersion) 77.22.Ch (Permittivity (dielectric function)) 78.20.Ci (Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity))