Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan.
Sci Rep. 2017 Aug 21;7(1):8357. doi: 10.1038/s41598-017-08354-7.
The problem of the ballistic electron tunneling is considered in magnetic tunnel junction with embedded non-magnetic nanoparticles (NP-MTJ), which creates additional conducting middle layer. The strong temperature impact was found in the system with averaged NP diameter d < 1.8 nm. Temperature simulation is consistent with experimental observations showing the transition between dip and classical dome-like tunneling magnetoresistance (TMR) voltage behaviors. The low temperature approach also predicts step-like TMR and quantized in-plane spin transfer torque (STT) effects. The robust asymmetric STT respond is found due to voltage sign inversion in NP-MTJs with barrier asymmetry. Furthermore, it is shown how size distribution of NPs as well as quantization rules modify the spin-current filtering properties of the nanoparticles in ballistic regime. Different quantization rules for the transverse component of the wave vector are considered to overpass the dimensional threshold (d ≈ 1.8 nm) between quantum well and bulk-assisted states of the middle layer.
研究了嵌入非磁性纳米颗粒（NP-MTJ）的磁性隧道结中弹道电子隧穿的问题，这会产生额外的中间导电层。在平均 NP 直径 d < 1.8nm 的系统中发现了强烈的温度影响。温度模拟与实验观察一致，表明在磁隧道电阻（TMR）电压行为的双极和经典穹顶之间存在转变。低温方法还预测了阶跃式 TMR 和量子化的面内自旋转移扭矩（STT）效应。由于势垒不对称的 NP-MTJ 中的电压符号反转，发现了稳健的不对称 STT 响应。此外，还展示了如何通过 NPs 的尺寸分布以及量子化规则来改变中间层弹道区中纳米颗粒的自旋电流滤波特性。为了超过中间层的量子阱和体辅助态之间的尺寸阈值（d ≈ 1.8nm），考虑了横向波矢分量的不同量子化规则。
