论文标题
隧道连接中的旋转扭矩和磁性抗性的自谐计算和具有金属针孔缺陷的磁性读数
Self-Consistent Computation of Spin Torques and Magneto-Resistance in Tunnel Junctions and Magnetic Read-Heads with Metallic Pinhole Defects
论文作者
论文摘要
开发了三维自搭配的自旋传输模型，其中包括隧道运输和金属传输。使用计算的隧道屏障两侧的自旋蓄积，获得了自旋扭矩，并显示模型均以预期的正弦角依赖性以及逆非磁性层依赖性依赖性依赖于阻尼状和场状的自旋转移扭矩。得出了对漂移扩散模型的明确解决方案，该解决方案允许分析参考层和自由层厚度对自旋转移扭矩极化和磁场状系数的影响。特别是，当层薄时，由于不完全吸收横向自旋成分，额外的自旋依赖性散射贡献减少了阻尼状和磁场状的自旋扭矩。它显示了此处开发的模型可用于计算逼真的磁性读取头的信噪比，在此磁性读取头上，旋转扭矩诱导的波动和不稳定性限制了最大工作电压。还分析了绝缘子层中金属针孔缺损的影响，这导致金属和隧穿传输的混合物以及高度不均匀的电荷和自旋电流，需要完整的自旋传输模型来计算产生的磁耐耐药性和旋转托架。在逆向依赖性后，磁铁抗性的覆盖面积增加导致磁抵抗的迅速降解。此外，自旋扭矩角依赖性偏向，并且自旋转移扭矩极化减小。当考虑具有单个针孔缺陷的隧道连接时，获得了相同的结果，但横截面区域减少，表明即使是单个针孔缺陷也可以显着降低40 nm节点下方的隧道连接和磁性读数头的性能。
A three-dimensional self-consistent spin transport model is developed, which includes both tunnelling transport, as well as metallic transport. Using the spin accumulation computed either side of a tunnel barrier, spin torques are obtained, and it is shown the model reproduces both damping-like and field-like spin-transfer torques, with the expected sinusoidal angular dependence, and inverse ferromagnetic layer thickness dependence. An explicit solution to the drift-diffusion model is derived, which allows analysing the effect of both the reference and free layer thickness on the spin-transfer torque polarization and field-like coefficient. In particular, when the layers are thin, additional spin-dependent scattering contributions due to incomplete absorption of transverse spin components reduce both the damping-like and field-like spin torques. It is shown the model developed here can be used to compute the signal-to-noise ratio in realistic magnetic read-heads, where spin torque-induced fluctuations and instabilities limit the maximum operating voltage. The effect of metallic pinhole defects in the insulator layer is also analysed, which results in a mixture of metallic and tunnelling transport, and highly non-uniform charge and spin currents, requiring the full spin transport model to compute the resulting magneto-resistance and spin torques. Increasing the area covered by pinholes results in a rapid degradation of the magneto-resistance, following an inverse dependence. Moreover, the spin torque angular dependence becomes skewed, and the spin-transfer torque polarization decreases. The same results are obtained when considering tunnel junctions with a single pinhole defect, but decreasing cross-sectional area, showing that even a single pinhole defect can significantly degrade the performance of tunnel junctions and magnetic read-heads below the 40 nm node.
