Inelastic scattering approach to the theory of a tunnel magnetic transistor source

The high efficiency of a tunnel magnetic transistor as a source of spin-polarized electrons has been proven recently [X. Jiang {\it et al.}, Phys. Rev. Lett. {\bf 90}, 256603 (2003)]. A concept of this device based on an active group of hot electrons controlling the collector current and experiencing predominantly inelastic scattering in the base is developed. It takes into account the interconnection between the injection and filtering of spin-polarized electrons in different elements of the device. Explicit expressions for the parameters of the device in terms of the basic parameters of the system are presented.