Raman spectra of Cu_2B~ⅡC~ⅣX_4~Ⅵ magnetic quaternary semiconductor compounds with tetragonal stannite type structure

摘要

A comparative study of the Raman spectra of Cu_2B~ⅡC~ⅣS_4~Ⅵ and Cu_2B~ⅡC~ⅣSe_4~Ⅵ(where B = Mn or Fe) magnetic quaternary semiconductor compounds with stannite-type structure (I42m) has been done. Most of the fourteen Raman lines expected for these materials were observed in the spectra. The two strongest lines observed have been assigned to the IR inactive A)1 and A]2 stannite modes that originated from the motion of the S or Se anion around the Cu and CIV cations remaining at rest. The shift in the frequency of these two lines of about 150 cm"1 to lower energies observed in Cu_2B~ⅡC~ⅣSe_4~Ⅵ compounds as compared to those in Cu_2B~ⅡC~ⅣS_4~Ⅵ ones, can then be explained as due to the anion mass effect. Based on the fact that values of these frequencies depend mainly on anion mass and bond-stretching forces between nearest-neighbor atoms, the vibrational frequencies ν(A_1~2) and ν(A_1~2) of both modes for several Cu_2B~ⅡC~ⅣX_4~Ⅵ stannite compounds (where X = S, Se, or Te) very close to the experimental data reported for these materials were calculated from a simple model that relates these stretching forces to the anion-cation bond-distances.