The effect of magnetic field on a nonballistic spin field effect transistor.

A spin field effect transistor (FET) made of a nonballistic quantum wire with a single transport channel is considered in the presence of a magnetic field. The magnetic field includes either the externally applied field or the stray field due to ferromagnetic contacts used as injector and collector. When a magnetic field is applied the conductance fluctuations alter the spin precession and moreover spin flip occurs if the magnetic field is perpendicular to the Rashba field. Necessary conditions for a successful spin FET operation is obtained in the presence of a magnetic field.