講演情報
[25a-P01-51]Spin-orbit-torque-induced magnetization switching in 75o-canted MTJ
〇Anh ThiVan Nguyen1,2, Hiroshi Naganuma1,2,3,4, Hiroaki Honjo2, Shoji Ikeda1,2, Tetsuo Endoh1,2,5,6 (1.CSIS, Tohoku Univ., 2.CIES, Tohoku Univ., 3.NAIAS, Nagoya Univ., 4.IMaSS, Nagoya Univ., 5.ECEI, Tohoku Univ., 6.RIEC, Tohoku Univ.)
キーワード：
SOT-MRAM、Ultrafast switching、Canted MTJ
SOT-induced magnetization switching has been widely investigated for high-performance MRAMs. So far, we have demonstrated the 0.35 ns field-free switching in canted SOT devices with 88 nm x 315 nm MTJ. For the SRAM replacement, a faster switching time and a lower switching current in a smaller MTJ are required for the low power consumption and high-density MRAM. Thus, a thoughtful simulation is necessary to support the experimental results efficiently. Herein, we investigate the change in SOT-induced magnetization switching in a 75deg-canted MTJ against a channel line by using micro-magnetic simulations under the influence of the effective anisotropy (Hk), and the field-like coefficient (b), i.e., the ratio between the field-like torque and the Slonczewski-like torque. The 10 nm x 30 nm elliptic MTJ device model was designed so that the current was applied in a direction that was 75deg-canted along the long axis of the MTJ. The free layer has an in-plane easy axis with an effective out-of-plane magnetic anisotropy field of Hk, including the bulk anisotropy field, the interfacial anisotropy field, and the demagnetization field. Fig. 1 (a) shows the time evolution of the magnetization for two devices with Hk = -0.9 T and Hk = -0.08 T. The switching time (t) is when the magnetization of the free layer is switched from the P state to the AP state. t for the former is 0.32 ns while t for the latter is 0.19 ns. As a result, the voltage for the P-AP switching at a pulse width of 0.35 ns in the latter (0.205 V) is 30% smaller than that for the former (0.295 V) (Fig. 1 (b)). Fig. 1 (c) shows the b dependence of t for two devices. When b increases, t decreases and can be reduced to 0.03 ns by increasing b to 1 in the device with Hk = - 0.08 T. To achieve the same result in the device with Hk = - 0.9 T, b must be increased to 6. These results indicate a way to achieve ultrafast field-free SOT switching of a few tens of ps in nm-sized MTJ devices.