Effects due to spin ordering in layered MPX3compounds revealed by inelastic light scattering

Abstract

Light scattering experiments on MPX3 compounds with M identical to Fe, Ni or Zn and X identical to S or Se and their MxM1-x'PX3 alloys at temperature ranging from 5 to 300K are presented. The peaks observed at room temperature are attributed to Raman-active normal modes of vibrations. Below the Neel temperatures of the iron and nickel antiferromagnetic compounds, three classes of effects are observed: (i) effects due to the appearance of a magnetic superstructure, which is different from the crystallographic cell and which induces Brillouin zone folding; (ii) effects due to spin-spin coupling evidenced by the temperature dependence of the integrated phonon Raman intensity which follows the reduced nearest-neighbour spin correlation function; (iii) effects due to the interference between single-phonon states and spin-split-off electronic bands. These effects are observed in the NiPS3 low-temperature spectrum which shows a broad Raman background on which are superimposed the phonon peaks undergoing lineshape deformations and antiresonance.