Department of Materials and Nano Physics, School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden.
Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Nanoscale. 2017 Feb 2;9(5):1896-1900. doi: 10.1039/c6nr07309c.
Spin torque nano-oscillators (STNO) represent a unique class of nano-scale microwave signal generators and offer a combination of intriguing properties, such as nano sized footprint, ultrafast modulation rates, and highly tunable microwave frequencies from 100 MHz to close to 100 GHz. However, their low output power and relatively high threshold current still limit their applicability and must be improved. In this study, we investigate the influence of the bottom Cu electrode thickness (t) in nano-contact STNOs based on Co/Cu/NiFe GMR stacks and with nano-contact diameters ranging from 60 to 500 nm. Increasing t from 10 to 70 nm results in a 40% reduction of the threshold current, an order of magnitude higher microwave output power, and close to two orders of magnitude better power conversion efficiency. Numerical simulations of the current distribution suggest that these dramatic improvements originate from a strongly reduced lateral current spread in the magneto-dynamically active region.
自旋扭矩纳米振荡器 (STNO) 代表了一类独特的纳米级微波信号发生器，具有引人注目的特性组合，例如纳米级尺寸、超快速调制速率以及可从 100MHz 调谐至接近 100GHz 的高度可调谐微波频率。然而，其低输出功率和相对较高的阈值电流仍然限制了它们的适用性，需要加以改进。在本研究中，我们研究了基于 Co/Cu/NiFe GMR 叠层的纳米接触 STNO 中底部 Cu 电极厚度 (t) 的影响，纳米接触直径范围为 60nm 至 500nm。将 t 从 10nm 增加到 70nm，可将阈值电流降低 40%，微波输出功率提高一个数量级，功率转换效率提高近两个数量级。电流分布的数值模拟表明，这些显著的改进源于磁动力学活性区域中横向电流扩散的大幅减少。
