自旋注入效率的电学探测

Electric detection of spin injection efficiency

为了探测从铁磁FM(ferrom agnet)到半导体SM(sem iconductor)的自旋注入效率,可以通过增加另一个铁磁体来形成一个铁磁/半导体/铁磁(FM/SM/FM)的双结,通过直接测量此双结的磁阻效应,从而得到从铁磁(FM)到半导体(SM)节的自旋注入效率。理论分析发现其隧道磁阻TMR(tunnelling m agnetoreresistance)和自旋注入效率SIE(sp in in jection efficiency)之间有个普适关系:隧道磁阻是自旋注入效率的平方。这种平方关系在顺序隧穿区和散射区都成立,除非双结间半导体层厚度很长导致自旋翻转效应的发生或中间的半导体层厚度小于其相位相干长度而导致磁阻中出现量子相干效应。

In order to detect spin injection efficiency from ferromagnet into semiconductor,another ferromagnet would be used to form a ferromagnet/semiconductor/ferromagnet double junction and directly measure the magnetoresistance effect to determine spin injection efficiency from ferromagnet into semiconductor. A general relation between them is found that the magnitude of magnetoresistance is the square of that of spin injection efficiency by theory analysis. The square relation is not only valid in the sequential tunneling regime but also in the diffusive regime, unless the spin flip effect occurs due to the long semiconductor layer in double junction,or the quantum interference takes an effect on the magnetoresistance when the length of semiconductor layer is less than the phase coherence length.