Kaiju Hideo, Misawa Takahiro, Nagahama Taro, Komine Takashi, Kitakami Osamu, Fujioka Masaya, Nishii Junji, Xiao Gang
Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido, 001-0020, Japan.
Graduate School of Engineering, Hokkaido University, Sapporo, Hokkaido, 060-8628, Japan.
Sci Rep. 2018 Oct 2;8(1):14709. doi: 10.1038/s41598-018-33065-y.
One of the most important achievements in the field of spintronics is the development of magnetic tunnel junctions (MTJs). MTJs exhibit a large tunneling magnetoresistance (TMR). However, TMR is strongly dependent on biasing voltage, generally, decreasing with applying bias. The rapid decay of TMR was a major deficiency of MTJs. Here we report a new phenomenon at room temperature, in which the tunneling magnetocapacitance (TMC) increases with biasing voltage in an MTJ system based on CoFeB/MgO/CoFeB. We have observed a maximum TMC value of 102% under appropriate biasing, which is the largest voltage-induced TMC effect ever reported for MTJs. We have found excellent agreement between theory and experiment for the bipolar biasing regions using Debye-Fröhlich model combined with quartic barrier approximation and spin-dependent drift-diffusion model. Based on our calculation, we predict that the voltage-induced TMC ratio could reach 1100% in MTJs with a corresponding TMR value of 604%. Our work has provided a new understanding on the voltage-induced AC spin-dependent transport in MTJs. The results reported here may open a novel pathway for spintronics applications, e.g., non-volatile memories and spin logic circuits.
自旋电子学领域最重要的成就之一是磁隧道结（MTJ）的发展。MTJ表现出很大的隧道磁电阻（TMR）。然而，TMR强烈依赖于偏置电压，一般来说，随着施加偏置而减小。TMR的快速衰减是MTJ的一个主要缺陷。在此，我们报道了一种室温下的新现象，即在基于CoFeB/MgO/CoFeB的MTJ系统中，隧道磁电容（TMC）随偏置电压增加。我们在适当偏置下观察到最大TMC值为102%，这是MTJ中报道过的最大的电压诱导TMC效应。我们发现，使用德拜 - 弗罗利希模型结合四次势垒近似和自旋相关漂移扩散模型，在双极偏置区域理论与实验结果高度吻合。基于我们的计算，我们预测在TMR值为604%的MTJ中，电压诱导的TMC比率可达到1100%。我们的工作为MTJ中电压诱导的交流自旋相关输运提供了新的理解。这里报道的结果可能为自旋电子学应用，如非易失性存储器和自旋逻辑电路，开辟一条新途径。
