International Conference on Phonon Physics

J. Phys. Colloques 42 (1981) C6-392-C6-394
DOI: 10.1051/jphyscol:19816114

RAMAN SCATTERING IN V₃Si, V₃Ge, Nb₃Sb, AND Cr₃Si : CORRELATION OF E_g OPTICAL PHONON LINEWIDTH WITH MAGNETIC SUSCEPTIBILITY

R. Merlin^{1, 2}, S.B. Dierker¹, M.V. Klein¹, J. Jørgensen³, S.R. Rasmussen³, Z. Fisk⁴ et G.W. Webb<sup>4

1</sup>  Department of Physics and Materials Research Laboratory, 104 S. Goodwin, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, U.S.A.
²  Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, U.S.A.
³  Department of Inorganic Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark.
⁴  Institute for Pure and Applied Life Sciences, University of California at San Diego, La Jolla, California 92093, U.S.A.

Abstract
Raman scattering measurements of the E_g optical phonon in V₃Si and Nb₃Sn show it to have an anomalous width, temperature dependence, and asymmetric lineshape. We have observed a similar, although weaker, anomaly in V₃Ge. The E_g and T_2g phonons in Nb₃Sb and the T_2g phonon in Cr₃Si show no anomalous behavior and can be understood in terms of simple anharmonic interactions. In Cr₃Si the E_g phonon has an anomalous width, shape, and temperature dependence (similar to V₃Ge) in spite of its low electronic density of states and temperature independent magnetic susceptibility. A linear correlation is shown to exist between magnetic susceptibility and E_g mode linewidth, Ɖ, in V₃Si, Nb₃Sn, and V₃Ge. With the aid of a simple model, most of the features of the Raman data can be understood in terms of direct coupling of the E phonon to interband electronic transitions between the very flat bands emanating from the Ɖ₁₂ level in these compounds. These results indicate that direct coupling of the E_g optical phonon to the Ɖ₁₂ bands plays a major role in the splitting of the cubic Ɖ₁₂ subband N(E) peak by the dimerization of the transition metal sublattice.