Anisotropy of phonon modes in spontaneously ordered GaInP2 -: art. no. 235205

초록

The anisotropy associated with angular variation of the phonon wave vector q with respect to the ordering axis z' of a spontaneously ordered GaInP2 with order parameter eta congruent to0.46 is studied by carefully performing micro-Raman measurements in scattering geometries where q is either parallel or perpendicular to z'. The LO mode at similar to 380 cm(-1) and the TO mode at similar to 330 cm(-1) exhibit distinct phonon frequency shifts of - 1.2 cm(-1) and +2.1 cm(-1), respectively, as the angle phi between q and z' varies from 0 degrees to 90 degrees. This small angular dispersion is explained on the basis of the bond-stiffening along the ordering axis with increasing order parameter eta, providing strong evidence for a small A(1)-E splitting in comparison to the large LO-TO splitting for these modes. In addition, an even larger angular dispersion, +2.5 cm(-1), for the vibrational mode at similar to 354 cm(-1) is observed. Two additional phonon modes, which have previously been labeled as missing to account for all nine Raman-active optical modes, are observed and experimentally identified with E(x) and E(y) tensors.

키워드