Spin injection from Co2MnGa into an InGaAs quantum well

Abstract

We have demonstrated spin injection from a full Heusler alloy Co2MnGa thin film into a (100) InGaAs quantum well in a semiconductor light-emitting diode structure at a temperature of 5K. The detection is performed in the oblique Hanle geometry, allowing quantification of the effective spin lifetime and spin detection efficiency (22±4%). This work builds on existing studies on off-stoichiometric Heusler injectors into similar light-emitting-diode structures. The role of injector stoichiometry can therefore be quantitatively assessed with the result that the spin injection efficiency increases by a factor of approximately 2 as compared with an off-stoichiometric Co2.4Mn1.6Ga injector.

InGaAs spin light emitting diodes measured in the Faraday and oblique Hanle geometries

“…A second system was used to measure the devices in the oblique Hanle geometry, where a small magnetic field is applied at an angle (ϕ) to the normal to the sample [7,14,16] , where Ω is the Larmor frequency and τ s is the spin lifetime. In both cases the optical polarization efficiency of the measured light is defined as Figure 2 shows the polarization of the emitted light as a function of magnetic field in the Faraday geometry (magnetic field parallel to the light k vector), with all points measured at 1.43 eV, the peak of the quantum well emission at zero magnetic field in this device.…”

“…Measuring the polarization across the interface between the polarized injector material and the semiconductor structure plays an important role in materials selection. The interface plays an essential role as evidenced by the fact that half-metallic materials (with bulk polarization approaching 100%) do not translate into equivalent high spin polarizations when combined with GaAs devices [7,8]. Fe spin-injecting contacts, with a bulk polarization of ~40%, have provided the highest spin-injection polarizations of all the simple metals.…”

Thin films of the Heusler alloys Cu2MnAl and Co2MnSi: recovery of ferromagnetism via solid-state crystallization from the x-ray amorphous state

“…ferromagnets with full spin polarization at the Fermi levelare promising materials for applications in spintronics [11,12]. They can be employed as spin filters [13], in spin injection/detection devices [14,15] or in magnetic tunnelling junctions (MTJs) [16]. Apart from a few oxidic compounds and Mn-doped semiconductors [17][18][19], the class of Heusler alloys provides the only metallic alloy system with halfmetallicity.…”

Hybrid Spintronic Structures With Magnetic Oxides and Heusler Alloys

“…A Co MnGe Heusler alloy spin LED [30] had an efficiency of 27%, which represents the limiting value with an epitaxial Heusler alloy even when the band structure is predicted to be half metallic. In more recent stoichiometric Co MnGa structures [31], the spin-injection efficiency is 22%. This lower than expected spin-injection efficiency is correlated with the reduced interface magnetization as observed from the XMCD and VSM measurements.…”