Spin injection across magnetic/non-magnetic interfaces with finite magnetic layers

TL;DR

This paper revisits spin injection across magnetic/non-magnetic interfaces with finite magnetic layers, providing new resistance expressions and analyzing the impact of contact magnetoresistance on observed spin-accumulation effects.

Contribution

It introduces revised formulas for resistances in structures with finite magnetic layers, differing from previous literature, and clarifies the role of contact magnetoresistance in spin-accumulation phenomena.

Findings

Resistances differ from previous models due to boundary condition adjustments.

Spin-accumulation alone cannot explain the $d$ dependence in data when contact magnetoresistance is negligible.

Finite magnetic layers can induce a strong $d$ dependence if contact magnetoresistances are sizable.

Abstract

We have reconsidered the problem of spin injection across ferromagnet/non-magnetic-semiconductor (FM/NMS) and dilute-magnetic-semiconductor/non-magnetic-semiconductor interfaces, for structures with \textit{finite} magnetic layers (FM or DMS). By using appropriate physical boundary conditions, we find expressions for the resistances of these structures which are in general different from previous results in the literature. When the magnetoresistance of the contacts is negligible, we find that the spin-accumulation effect alone cannot account for the $d$ dependence observed in recent magnetoresistance data. In a limited parameter range, our formulas predict a strong $d$ dependence arising from the magnetic contacts in systems where their magnetoresistances are sizable.