Raman scattering from magnons and phonons in the mixed antiferromagnet Fe1-xMnxCl2

Abstract
Magnons and phonons in the mixed crystal Fe1-xMnxCl2 have been studied by Raman scattering techniques. The k=0 Fe2+ magnon-like excitations have been observed for T0.15. For the mixed crystals an Ising cluster model is proposed and discussed in terms of the observed concentration dependence of the magnon energy. The temperature and concentration dependences of the two Raman-active k=0 phonons have been analysed over the whole concentration range. The A1g phonon frequency exhibits a linear concentration dependence in accordance with the predicted one-mode behaviour, whereas the Eg phonon behaviour is more complicated for <or approximately=0.6 because of electron-phonon coupling.