Improvement of Write Efficiency in Voltage-Controlled Spintronic Memory by development of a Ta- B Spin Hall Electrode

Improving the write efficiency of magnetic tunnel junctions (MTJs) by using spin-orbit torque (SOT) is essential for realizing high-density spintronic memory. Here, we investigate a voltage-controlled spintronic memory (VoCSM) with a Ta-B spin Hall electrode. The magnetic properties of MTJs with a storage layer such as Fe-B or Co-Fe-B on an amorphous boride spin Hall electrode are found to exhibit an extremely small magnetic dead layer, a small saturation magnetization, and a large magnetic anisotropy. The spin Hall angle estimated by spin Hall magnetoresistance is -0.18 for the amorphous Ta-B spin Hall electrode, which is a magnitude twice that for a Ta spin Hall electrode. The write current density using SOT from the Ta-B spin Hall electrode is small compared with that from the β-Ta spin Hall electrode. By combining the self-aligned fabrication technique with the Ta-B electrode, a small value of critical switching current (Ic≈79μA) is achieved despite a large MTJ size (60×150nm2). We successfully reduce the write current to 48 μA, utilizing a voltage-controlled magnetic anisotropy by applying the voltage to a MTJ: VMTJ=-1V. Moreover, the device also exhibits a low write error rate (<1×10-8), high endurance (>1×1012 cycles), and large break-down voltage (>2.5V). These results indicate that VoCSM with the Ta-B spin Hall electrode could open a path to realizing high-density nonvolatile memories with low power consumption and high-speed read and write operations.