The spin polarisation of conduction electrons in a ferromagnetic semiconductor

It is argued that the 'multiband' model of Nolting (1979, 1980) for the conduction band of a ferromagnetic semiconductor is unrealistic and cannot provide a correct explanation of the spin polarisation of field-emitted electrons from a W-EuS junction. A simple theory is given which shows that the polarisation should be approximately proportional to the magnetisation of the EuS, in reasonable agreement with experiment.