Spin injection efficiency from two adjoining ferromagnetic metals into a two-dimensional electron gas

TL;DR

This paper investigates how adding a second ferromagnetic metal and tunnel barriers in a ballistic junction can significantly enhance and control spin injection efficiency into a two-dimensional electron gas, with potential applications in spintronic devices.

Contribution

It introduces a novel FM/I/FM/I/2DEG junction model and demonstrates quantum interference effects that enable high and tunable spin injection efficiency.

Findings

Spin polarization oscillates with FM layer thickness and exchange energy.

Maximum spin injection efficiency exceeds 80%.

Electron density influences the polarization control.

Abstract

In order to enhance spin injection efficiency from ferromagnetic (FM) metal into a two-dimensional electron gas (2DEG), we introduce another FM metal and two tunnel barriers (I) between them to investigate the current polarization in such ballistic FM/I/FM/I/2DEG junction. Our treatment is based on the free-electron scattering theory. It is found that due to quantum interference effect, the magnitude and sign of the current polarization exhibits periodical oscillating behavior with variation of the thickness of the middle FM metal layer or its exchange energy strength. For some suitable parameters, the spin injection efficiency may arrive over 80% in this junction and can also be controlled by the electron density of 2DEG. Our results may shed light on the development of new spin-polarized device.