论文标题
COFE/MGO/COFE（001）连接处的巨型振荡隧道磁力
Giant oscillatory tunnel magnetoresistance in CoFe/MgO/CoFe(001) junctions
论文作者
论文摘要
在磁性隧道连接（MTJ）中观察到的隧道磁磁性（TMR）效应通常用于许多自旋应用应用中，因为该效果可以轻松地从局部磁性状态转换为具有广泛设备电阻的电信号。在这项研究中，我们在室温（RT）（RT）时证明了高达631％的TMR比，使用COFE/MGO/COFE（001）外延MTJ，比当前用于磁倍率的随机访问记忆（MRAM）设备的TMR比率大两倍或多倍。 TMR比在10 K时增加到1143％，这对应于有效的隧穿自旋极化为0.923。观察到的较大的TMR比是由MTJ的原子尺度结构进行的微调，例如晶体学方向和MGO界面氧化，其中巨大TMR效应的众所周知的Delta1相干隧道机制有望发音。但是，标准相干隧道理论不涵盖的行为出乎意料地表现出来。即，（i）在厚的MgO屏障区域和（ii）以0.32 nm周期为MGO厚度的TMR饱和度。特别是，TMR振荡行为在广泛的MGO厚度中占主导地位。 TMR振荡的峰值到valley在RT时的峰值差异超过140％，这归因于电阻区产品（RA）中大型振荡成分的出现。此外，我们发现，即使在 +-1 V偏置电压施用下，TMR比和RA的振荡行为也可以生存，这表明振荡的稳健性。我们对巨型RT-TMR比率的演示将是建立Spintronic体系结构的重要步骤，例如大容量MRAM和Spintronic人工神经网络。从本质上讲，目前的观察结果可能会触发我们重新审视Crystaline MTJ中真正的TMR机制。
The tunnel magnetoresistance (TMR) effect observed in magnetic tunnel junctions (MTJs) is commonly used in many spintronic applications because the effect can easily convert from local magnetic states to electric signals in a wide range of device resistances. In this study, we demonstrated TMR ratios of up to 631% at room temperature (RT), which is two or more times larger than those used currently for magnetoresistive random access memory (MRAM) devices, using CoFe/MgO/CoFe(001) epitaxial MTJs. The TMR ratio increased up to 1143% at 10 K, which corresponds to an effective tunneling spin polarization of 0.923. The observed large TMR ratios resulted from the fine-tuning of atomic-scale structures of the MTJs, such as crystallographic orientations and MgO interface oxidation, in which the well-known Delta1 coherent tunneling mechanism for the giant TMR effect is expected to be pronounced. However, behavior that is not covered by the standard coherent tunneling theory was unexpectedly manifested; i.e., (i) TMR saturation at a thick MgO barrier region and (ii) enhanced TMR oscillation with a 0.32 nm period in MgO thickness. Particularly, the TMR oscillatory behavior dominates the transport in a wide range of MgO thicknesses; the peak-to-valley difference of the TMR oscillation exceeded 140% at RT, attributable to the appearance of large oscillatory components in resistance area product (RA). Further, we found that the oscillatory behaviors of the TMR ratio and RA survive, even under a +-1 V bias voltage application, indicating the robustness of the oscillation. Our demonstration of the giant RT-TMR ratio will be an essential step for establishing spintronic architectures, such as large-capacity MRAMs and spintronic artificial neural networks. More essentially, the present observations can trigger us to revisit the true TMR mechanism in crystalline MTJs.
