Spin transport theory in ferromagnet/semiconductor systems with noncollinear magnetization configurations

We present a comprehensive theory of spin transport in a nondegenerate semiconductor that is in contact with multiple ferromagnetic terminals. The spin dynamics in the semiconductor is studied during a perturbation of a general, noncollinear magnetization configuration and a method is shown to identify the various configurations from current signals. The conventional Landauer-B\"uttiker description for spin transport across Schottky contacts is generalized by the use of a nonlinearized I-V relation, and it is extended by taking into account noncoherent transport mechanisms. The theory is used to analyze a three terminal lateral structure where a significant difference in the spin accumulation profile is found when comparing the results of this model with the conventional model.