Research Of Tunneling Magnetoresistance Effect In Ferromagnet/Semiconductor/Ferromagnet System

In the late 80s, people found that there existed interlayer coupling effect and giant magnetoresistance in FM/NM multilayer within nano-scale, on the base of which, the spin valve resistor was developed to become the hot of the storing medium because of its high sensitivity in low magnetic fields. In 1975 Julliere found that there existed giant magnetoresistance effect in Fe/Ge/Co tunnel junction and then called it as tunnel magnetoresistance(TMR). Compared with normal metal multilayer film, this kind of tunnel junction with ferromagnet/insulator/ferromagnet structure has the characteristic of high inside resistance, low consumption and high output voltage. And its magnetoresistance ratio is theoretically predicted to reach 20 to 50%, which is bigger than that of spin valve film. So the tunnel junctions have good potential for use in high density magnetic random access memorizer.In this paper, We introduced firstly the giant magnetoresistance and the tunneling magnetoresistance. Then we studied theoretically the tunnel magneto-resistance in a ferromagnet/semiconductor/ferromagnet junction including doubleδbarriers and double schottky barriers respectivly with quantum mechanical approach. The investigations were based on the Slonczwski model. For the first case, eachδbarrier is formed between a semiconducting material and a ferromagnetic material. The results showed that TMR strongly depends on the angle of molecular field. The TMR reachs minimums when the magnetic moments of the two electrodes are parallel each other (θ= 0.(?)=0 andθ=π, (?)=π). The maximums appear whenθequal 0 and (?) equalπ, the magnetic moments of both electrodes are antiparallel each other. The TMR decreases with increase of the parameter of barrier. When the Rashba spin-orbit interaction increases, The variation of TMR strongly depends on the angle of molecular field. In the second case, each schottky barrier is formed between a semiconducting material and a ferromagnetic material. The results of investigation showed that the TMR varies periodically from 0 to 2πwith increase of the angle of magnetic metal electrode. The TMR reachs maximums when the magnetic moments of the two electrodes are antiparallel each other(θ=π); The TMR reachs minimums when the magnetic moments of the two electrodes are parallel each other(θ=0,θ=2π). When the Rashba spin-orbit interaction increases, the TMR decreases. The TMR increases along with increase of the barrier height.The TMR depends on the barrier shape. It is more accurate that a schottky barrier is formed between a semiconducting material and a ferromagnetic material. Our above work is expected to be helpful for the developing new giant magne-toresistance devices and the research about Spintronics.