Low-current-density spin-transfer switching in Gd22Fe78-MgO magnetic tunnel junction

Abstract

Magnetization switching of a relatively thick (9 nm) Gd-Fe free layer was achieved with a low spin injection current density of 1.0 × 106 A/cm2 using MgO based magnetic tunnel junction devices, fabricated for light modulators. At about 560 × 560 nm2 in size, the devices exhibited a tunneling magnetoresistance ratio of 7%. This low-current switching is mainly attributed to thermally assisted spin-transfer switching in consequence of its thermal magnetic behavior arising from Joule heating.

Two Micron Pixel Pitch Active Matrix Spatial Light Modulator Driven by Spin Transfer Switching

“…As displayed in Figure 7, the value of I d was 0.75 mA, which corresponds to 0.33 MA/cm 2 . In contrast, the required switching current density of the MTJ devices was 1.0 MA/cm 2 [13], this being a much greater current density than the transistor could provide. For this reason, we employed magnetic field-assisted STS in conjuction with the 2 µm pixel pitch spin-SLM.…”

“…Each drain terminal of the FET was connected to the pinned layer of the MTJ through a copper electrode, each of which was composed of a 100 × 100 electrode array. The MTJ device consisted of a pinned layer of Ru (3 nm)/Tb-Fe-Co (10 nm)/Co-Fe (0.5 nm), a 1 nm MgO insulating layer, and an LM layer of Co-Fe (0.25 nm)/Gd (0.2 nm)/Gd-Fe (9 nm)/Ru (3 nm), which were all deposited using an ion beam sputtering system [13]. Because the 100 × 100 spin-SLM comprises a large number of pixels, it is very important to obtain uniform MTJ properties.…”

“…As a transistor current supply capability for the STS is proportional to the transistor dimensions of the active matrix, it decreases with transistor size (narrow pitch). So far, we have developed an active matrix addressed spin-SLM (5 × 10 array layout with 5 µm pixel pitch), which is not a sufficiently small pixel pitch and relatively small scale in order to display an image with wide viewing zone [13,14]. Consequently, it is very important to develop spin-SLM with small pixel pitch and larger pixel format for the realization of electro-holography with a wide viewing zone.…”

Current-induced domain-wall motion in patterned nanowires with various Gd–Fe compositions for magneto-optical light modulator applications

“…13) However, we need to further reduce the switching current as the current supply from the backplane transistors has increasingly decreased with the development of a spin-SLM with 1 µm pixel pitch. We have already decreased the switching current density of the light modulation layer of MTJs for spin-SLM, 11) and further reduction would be very difficult with MTJs. On the other hand, recently, current inplane type devices have been developed, which are good for light modulator applications since their cross-sectional area is much smaller than that of CPP-type devices, such as currentinduced DW motion (CIDWM).…”

“…[1][2][3][4][5][6][7][8] A magneto-optical spatial light modulator (MO-SLM) has been investigated [9][10][11][12][13] to realize a holography display with magnetic tunneling junctions (MTJs) in which magnetization reversal is driven by spin-transfer torque (spin-SLM). 10,12,13) An optical-address type MO-SLM has also been studied.…”