Spin injection at remanence into III-V spin light-emitting diodes using (Co/Pt) ferromagnetic injectors

Abstract

We have studied the perpendicular magnetic anisotropy of Co/Pt multilayers and the electron spin injection efficiency by optical spectroscopy from a [Co(0.6 nm)/Pt(1 nm)] 4 /Fe(0.3 nm)/MgO perpendicular tunnel spin injector grown on AlGaAs/GaAs semiconductor light-emitting diodes. We observe a 2.5% circular polarization at low temperature close to the magnetic remanence when the 0.3 nm Fe film of the ferromagnetic injector is sufficiently thin to maintain the magnetization out of plane. The acquired squared magnetization cycle is explained by the remaining interlayer exchange coupling existing between Fe and the (Co/Pt) multilayer through Pt or possible perpendicular magnetic anisotropy at the MgO/Fe interface. The corresponding spin polarization of the current is then estimated as 7%, measured by photoluminescence techniques, after the necessary uprenormalization, taking into account the electron spin-flip rate in the quantum well. In contrast, no circular polarization is observed when the thin Fe layer is removed and despite the rather high magnetic polarizability of the 5d 9 electronic open shell of Pt at the interface with MgO. This emphasizes the reduced size of tunneling branching of wave functions at the interface, of the order of the atomic plane unit.

Dzyaloshinskii-Moriya interaction at disordered interfaces from ab initio theory: Robustness against intermixing and tunability through dusting

“…Secondly, the induced moments in the Pt-part are also enhanced and the decay into the Pt-bulk is slightly slower as compared to the clean interface. However, the induced Pt moments only contribute little to the total magnetic moment of the slab (around 2%), in accordance with previous studies 29 . All Co moments in the intermixed layers vary linearly as function of intermixing x (not shown).…”

Toward high-frequency operation of spin lasers

“…4). However, a perpendicular anisotropy could provide an elegant spin injection in remanence, [82][83][84] avoiding the technologically undesirable applied magnetic field. The progress in fast magnetization reversal could stimulate implementing all-electrical schemes for spin modulation in lasers that were shown to yield an enhanced bandwidth in lasers.…”

Large and robust electrical spin injection into GaAs at zero magnetic field using an ultrathin CoFeB/MgO injector

“…A prerequisite to obtain optimized device functionalities is to promote a robust perpendicular magnetic anisotropy (PMA) medium up to room temperature (RT) to be used as a solid-state ferromagnetic (FM) injector electrode. Good candidates are systems including alternated planes of 3d/4f Fe/Tb 19,20 , 3d/5d Co/Pt 21,22 , or 3d/3d Co/Ni multilayers 23 . However, these systems generally suffer from the requirement of a minimum thickness (generally several units of bilayers) grown on a thin oxide layer, which is used as a tunneling barrier to circumvent the conductivity mismatch between metal and semiconductor 24 .…”

“…95% light is absorbed for 40 nm Fe/Tb multilayers 19,20 . Moreover, in the case of spin-LEDs, there is also a requirement that the first FM atomic plane grown at the interface must possess a robust spin-polarization for an efficient spin-injection, which is hardly attainable due to the chemical inter-diffusion or intermixing in the multilayer systems 22 . Therefore, up to now, the circular polarization (P C ) of emitted light was still limited to 3-4% at remanence 20,22,25 We have investigated electrical spin injection from an ultrathin perpendicularly magnetized CoFeB contact (1.2 nm) into InGaAs/GaAs quantum wells (QWs) embedded spin-LED.…”