SPIN INJECTION - THEORY AND APPLICATION TO JOHNSONS SPIN SWITCH

We apply the formalism of the model worked out by Valet and Fert for p erpendicular transport in multilayers to the problem of Johnson's spin switch. We find that, when the spin relaxation in the ferromagnetic l ayers is taken into account, the output voltage does not diverge when the nonmagnetic thickness tends to zero, but tends to a constant value governed by the spin relaxation in the ferromagnet. We also find that there is complete correspondence between the theoretical expressions for Johnson's spin switch and CPP-MR of multilayers. However, comparin g and discussing experimental results on spin switch and CPP-MR struct ures leads to the puzzling result that the spin diffusion lengths requ ired to account for spin switch data are much larger than those derive d from CPP-MR measurements.