Deng Jiefang, Liang Gengchiau, Gupta Gaurav
Electrical and Computer Engineering, National University of Singapore, 117576, Singapore, Singapore.
Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, 117546, Singapore.
Sci Rep. 2017 Nov 29;7(1):16562. doi: 10.1038/s41598-017-16292-7.
Switching magnetization in a perpendicular magnetic tunnel junction (pMTJ) via voltage controlled magnetic anisotropy (VCMA) has shown the potential to markedly reduce switching energy. However, the requirement of an external magnetic field poses a critical bottleneck for its practical applications. In this work, we propose an elliptical-shaped pMTJ to eliminate the requirement of providing an external field by an additional circuit. We demonstrate that a 10 nm thick in-plane magnetized bias layer (BL) separated by a metallic spacer of 3 nm from the free layer (FL) can be engineered within the MTJ stack to provide the 50 mT bias magnetic field for switching. By conducting macrospin simulation, we find that a fast switching in 0.38 ns with energy consumption as low as 0.3 fJ at a voltage of 1.6 V can be achieved. Furthermore, we study the phase diagram of switching probability, showing that a pulse duration margin of 0.15 ns is obtained and low-voltage operation (~1 V) is favored. Finally, the MTJ scalability is considered, and it is found that scaling down may not be appealing in terms of both the energy consumption and the switching time for precession based VCMA switching.
通过电压控制磁各向异性（VCMA）在垂直磁隧道结（pMTJ）中切换磁化强度已显示出显著降低切换能量的潜力。然而，对外部磁场的需求成为其实际应用的关键瓶颈。在这项工作中，我们提出一种椭圆形pMTJ，以消除通过额外电路提供外部磁场的需求。我们证明，在MTJ堆栈中，可以设计一个10 nm厚的面内磁化偏置层（BL），它与自由层（FL）由3 nm的金属间隔层隔开，以提供用于切换的50 mT偏置磁场。通过进行宏自旋模拟，我们发现，在1.6 V电压下，可实现0.38 ns的快速切换，能耗低至0.3 fJ。此外，我们研究了切换概率的相图，结果表明可获得0.15 ns的脉冲持续时间裕度，并且有利于低电压操作（~1 V）。最后，考虑了MTJ的可扩展性，发现对于基于进动的VCMA切换，在能耗和切换时间方面，缩小尺寸可能并不具有吸引力。
