单自旋过滤隧道结中隧穿时间的研究

The tunneling time in FM/I/SF/NM spin filter tunnel junctions

基于自由电子近似和Winful的隧穿时间模型,研究了铁磁金属/非磁绝缘体/自旋过滤层/普通金属(FM/I/SF/NM)单自旋过滤隧道结中自旋相关的居留时间(Dwell Time)和相位时间(Phase Time).计算结果表明,和传统的FM/I/FM结构不同,由于SF层的作用,在SF层和FM层中分子场处于反平行排列时上下自旋电子的透射率并不相等.在高能区(入射能量大于势垒高度),由于自干涉项影响大大减小,不同自旋方向电子的相位时间和居留时间趋于相同.在低能区(入射能量小于势垒高度),自干涉项影响增大,不同自旋方向电子的相位时间和居留时间会出现差别.其中非磁绝缘层和自旋过滤层的势垒高度,自旋过滤层的宽度以及自旋过滤层中分子场的变化,会导致上自旋电子的相位时间和居留时间出现明显差距.而对于下自旋电子,其相位时间和居留时间的不同,主要由自旋过滤层相应参数的变化决定,非磁绝缘层势垒高度变化的影响较小.

Based on the free electronic model and the Winful＇s tunneling time theory, the spin dependent dwell time and the phase time in ferromagnetic metal/nonferromagnetic metal/spin filter layer/normal metal single spin filter tunneling junctions （FM/I/SF/NM） are investigated. The results show that, different from the traditional FM/I/FM structures, the transmission coefficients for up and down spin electrons are not equal due to the effects of the SF layer when the molecular fields in FM and SF layers are at antiparallel arrangement. With the higher incident electronic energies （the incident energies are higher than the barrier height）, as the decreasing influences of the self-interference delay, the phase times and the dwell times tend to same for different spin orientations electrons. But with the lower incident electronic energies （the incident energies are smaller than the barrier height）, as the increasing influences of the self-interference delay, the differences between the phase times and the dwell times appear for different spin orientations electrons. And, the barrier heights of the I and SF layers, and the widths and the molecular fields of spin filter barrier can induce large differences between the phase times and the dwell times for spin-up electrons. But for the spin-down electrons, the differences between the phase times and the dwell times are induced mainly by the changes of parameters of the SF layer and tinily by the varies of barrier heights of the I layer.