Electrical spin injection into GaAs based light emitting diodes using perpendicular magnetic tunnel junction-type spin injector

Abstract

Remanent electrical spin injection into an InGaAs/GaAs based quantum well light emitting diode is realized by using a perpendicularly magnetized MgO/CoFeB/Ta/CoFeB/MgO spin injector. We demonstrate that the Ta interlayer plays an important role to establish the perpendicular magnetic anisotropy and the thickness of Ta interlayer determines the type of exchange coupling between the two adjacent CoFeB layers. They are ferromagnetically or antiferromagnetically coupled for a Ta thickness of 0.5 nm or 0.75 nm, respectively. A circular polarized electroluminescence (Pc) of about 10% is obtained at low temperature and at zero magnetic field. The direction of the electrically injected spins is determined only by the orientation of the magnetization of the bottom CoFeB layer which is adjacent to the MgO/GaAs interface. This work proves the critical role of the bottom CoFeB/MgO interface on the spin-injection and paves the way for the electrical control of spin injection via magnetic tunnel junction-type spin injector.

Perpendicularly magnetized CoFeB multilayers with tunable interlayer exchange for synthetic ferrimagnets

“…Prior studies of a similar system have show that a magnetically dead layer can be formed at the Ta/CoFeB interface 7 . According to 6 , the effective magnetic CoFeB layer thickness d is significantly reduced compared to the nominally deposited thickness if t ≥ 0.5 nm. The estimated values for d based on the findings in 6 are given in Table I. III.…”

Remote microwave monitoring of magnetization switching in CoFeB/Ta/CoFeB spin logic device

“…The GaAs substrate was selected for easy integration into semiconductor based devices such as spin light emitting diode (LED) structures, 13,14 and for future semiconductor compatible applications in spintronics. Growth conditions are described in detail in Refs.…”

“…During this process, diffusing boron was absorbed by the 0.75 nm Ta interlayer, which also provided antiferromagnetic coupling between the two adjacent CoFeB layers. 13,14 To identify the switching sequence for bottom and top CoFeB layers from M-H curves, we performed the spin-LED measurement sensitive to the magnetization state of the bottom CoFeB layer only. In addition, the total magnetic dead layer is determined to be about 0.5 nm, which is almost equally distributed in both sides of the Ta insertion layer.…”

“…In addition, the total magnetic dead layer is determined to be about 0.5 nm, which is almost equally distributed in both sides of the Ta insertion layer. 13 The plate-shaped sample 0.4 Â 4 Â 4 mm 3 in size was studied in experiments. Both microwave magnetoresistance (MMR) and ferromagnetic resonance (FMR) signals were recorded using a Bruker ESP 300 X-band ESR spectrometer (microwave frequency: f 0 ¼ 9447 GHz, microwave power: 6.3 mW, modulation frequency: 100 kHz, modulation amplitude: 10 Oe, and quality factor: Q $ 4000).…”

Spin Injection From EuS/Co Multilayers Into GaAs Detected by Polarized Electroluminescence

“…The drawback of surface emitting experiments is the need for large external magnetic fields in order to saturate the sample magnetization, which is usually confined in the sample plane due to its anisotropy. Hence, measuring in remanence requires the use of magnetic systems with perpendicular magnetic anisotropy [30], [31]. In addition, light emitted parallel to the sample surface, i.e., from the sample side (side emission) does not show any polarized electroluminescence (EL) [32].…”