Infrared Lattice Vibrations and Dielectric Dispersion in Antiferromagnetic Semiconductor MnSe₂

Abstract

The infrared reflection spectrum of an antiferromagnetic semiconductor MnSe₂ was measured in the energy range 30∼1000 cm⁻¹, and four optical phonon modes were observed at 140 cm⁻¹, 157 cm⁻¹, 175 cm⁻¹, and 223 cm⁻¹. The optical constants were calculated by Kramers-Kronig analysis, and were also analyzed by the classical oscillator model. From these dielectric constants, the longitudinal and the transverse optical phonon frequencies were estimated. The Born and Szigeti effective charges were calculated and the ionicities among MnS₂, MnSe₂, MnTe₂ and FeS₂ were studied in relation to magnetic properties of these compounds. It is verified also that the generalized Lyddane-Sachs-Teller equation apply well to MnSe₂.