Electrical manipulation of magnetization switching in Co2FeAl alloy based magnetic tunnel junctions with in-plane and perpendicular magnetization
Electrical manipulation of magnetization switching, such as spin-transfer torque (STT) switching, electric-field-assistant magnetization switching, and spin-orbit torque (SOT) switching, has been attracting great attentions due to its applications in low-power-consumption spintronic devices, such as magnetoresistive random access memories (MRAMs) and non-volatile magnetic-logic circuits. Recent investigations of electrical manipulation of magnetization switching in magnetic tunnel junctions (MTJs) have mainly been carried out in CoFeB/MgO/CoFeB structures. However, the switching current density of those MTJs is still too high for the scaling of gigabit MRAMs. Therefore, the establishment of new ferromagnetic materials for MTJs is greatly desired.
Spin-transfer switching in full-Heusler Co2FeAl-based magnetic tunnel junctions
We demonstrated spin-transfer magnetization switching using magnetic tunnel junctions (MTJs) with a full-Heusler alloy Co2FeAl (CFA). We prepared CFA (1.5 nm)/MgO/CoFe (4 nm) (“CFA-free”) and CFA (30 nm)/MgO/CoFeB (2 nm) (“CFA-reference”) MTJs on a Cr(001) layer. The intrinsic critical current density (Jc0) of the CFA-free (CFA-reference) MTJ was 29 MA/cm2 (7.1 MA/cm2). The larger Jc0 of the CFA-free MTJ is attributed to the significant enhancement of the Gilbert damping factor (∼0.04) of the CFA due to the Cr layer. The Jc0 of the CFA-reference is as small as that reported for typical CoFeB/MgO/CoFeB MTJs.
Evaluation of Spin-Transfer Switching in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions
Current-induced magnetization switching was demonstrated on Co–Fe–B/MgO/Co–Fe–B magnetic tunnel junctions (MTJs), which exhibited giant tunnel magnetoresistance ratios of about 100%. Switching current density at a pulse duration of 100 ms was about 6×106 A/cm2 at room temperature. The switching current density was reduced to one-third of the smallest value for the MgO-based MTJs reported to date. Dependence of the switching current on pulse duration and on the external magnetic field was discussed based on a theoretical model incorporating thermally activated spin-transfer switching. The spin-transfer switching in the MgO-based MTJs realizes low writing power consumption and a high read-out signal in high-density magnetoresistive random access memory.