Raman scattering in the one-dimensional ferromagnet CsNiF3

Abstract

Reports phonon, magnon and high-energy (6800 to 14000 cm-1) electronic Raman scattering in CsNiF3. One-magnon scattering is observed with an applied magnetic field which ferromagnetically aligns the spins: both experimental frequency and selection rules for polarised spectra are interpreted. The high-energy electronic spectra involve transitions, within the Ni2+ ion (3d)8 configuration, from the 3A2g ground level to the 3T2g and 3T1ga excited states; each transition shows sharp zero-phonon electronic lines in addition to a broad phonon-assisted band. The widths and the peak positions of the sharp lines are related to spin correlation functions which depend upon the temperature and the applied magnetic field, as experimentally observed. The intensities of the polarised spectra are also discussed in terms of spin correlation functions for all the irreducible representations which can be assigned to the excited states.