With the aid of a hydrodynamic model of a plasma, a detailed analytical investigation is made of the Raman instability of the Stoke's component of the scattered wave in an obliquely magnetised (with respect to the direction of propagation) centrosymmetric semiconductor. The origin of the stimulated Raman scattering process lies in the third-order nonlinear optical susceptibility arising due to the induced nonlinear currently density and the interaction of the pump wave with the density fluctuations generated within the medium. The agreement in magnitude for third-order Raman susceptibility between our calculated values and the experimental as well as other theoretical values in found to be good. Using the couples mode theory of plasmas the total refractive index and absorption coefficient are determined via the effective susceptibility. The magnetic field and effective electric field are found to augment the refractive index. The absorption coefficient is found to be minimum when the pump is inclined at an angle of 12° to the magnetic field. The absorption coefficient reaches its minimum for the backscattered mode. The analysis establishes that a large nonlinear refractive index and a small absorption coefficient can easily be obtained in a magnetised centrosymmetric crystal which proves its potential as candidate material for fabrication of cubic nonlinear devices.