Tunneling Time In Spin-filter Tunnel Junctions

The recent experimental and theoretical studies show that using FM/I/SF/NM single spin filter tunnel junction and NM/SF/I/SF/NM double spin filter tunnel junction not only can get a great deal of TMR and spin polarization current,but also can overcome the shortcoming of conventional MTJ in which the TMR is decreased sharply with bias.As the spin-filter junctions have potential applications and significant values in the field of spin-polarized tunneling,the tunneling time of single and double spin-filter junctions are studied based on the previous studies.In this paper,the backgrounds about the magnetic tunnel junction and tunneling time are introduced firstly.Then,according the model suggested by the Winful and the Guo et al,the spin-dependent dwell times and phase times in single and double spin-filter junctions are calculated.The results show that,in the FM/I/SF/NM junctions,the dwell times and phase times for up and down spin electrons tend to be same when the incident electronic energies are larger than the potential heights(high energy regions).When the incident electronic energies are smaller than the potential height(low energy regions),the influence of the self-interference effect will become large and cause the obvious differences between the dwell times and the phase times for up and down spin electrons.At low energy regions,the difference between the dwell and phase times for up-spin electrons are obvious and these differences will increase with the increase of the widths and heights of the spinfilter barrier layers and remain unchanged in the last.For the down-spin electrons,the differences between the dwell times and the phase times are not obvious,but for the nonsymmetry case(the barrier heights for the I and SF layers are not same),the differences would be become large when the width,the potential height and the molecular field in the spin-filter layer increase.For the double spin-filter junctions,the most of the properties of dwell times and the phase times for up and down spin electrons are similar as the single spin-filter junctions.But one special characteristic in double spin-filter junctions is that the peaks will appeared in dwell and phase times when the potential heights of the spin-filter barrier and insulator barrier are varied.This phenomenon can be ascribed to the spin-dependent resonant tunneling.The above results would have helps for the future spin-devices studies and applications.