The Theoetical Research About The Tunneling Magnetoresistance In Magnetical Tunnel Junctions

In the 21st century, people's lives are being rapidly improved with the development of science and technology. The fabricated spintronic devices take use of the charge and the spin of electrons together to carry information and store information, which may gradually change the way to store information. The advantages of spintronic devices would be nonvolatility, increased integration densities, and decreased electric power consumption compared with conventional magnetic electronic devices. The very good application potentialities have been shown in magnetic record and magnetoresistive random access memory (MRAM). Because of unique properties, these novel spintronics materials, such as magnetic semiconductor, organic semiconductor, have become one of best candidates for spin polarized transport materials. It has a significant effect on the development of spintronics, understanding the physics of organic semiconductors to study spin polarized relaxation and transport properties in organic semiconductor materials.In this thesis, the main work and results are as follows:1. We selected a magnetic-semiconductor as an interlayer and investigated the electronic transport properties in the ferromagnetic/ferromagnetic-semiconductor/ferromagnetic (FM/FS/FM) trilayers. The results indicate that the large TMR comparable to that in ferromagnetic/metal oxide/ferromagnetic sandwich can be obtained in the FM/FS/FM multrilayers with considering the spin filter effect in the magnetic semiconductor layer. Moreover, the transmission coefficient and TMR can be tuned by some physical parameters, such as the thickness, Rashba spin-orbit coupling strength and molecular field of the magnetic semiconductor. Our calculations could provide a way to design the semiconductor spintronic devices with excellent and controllable properties.2. Based on Slonczewski's free-electron approximation and transfer matrix method, the temperature and/or bias-voltage dependence of the spin-polarized tunneling electrons in ferromagnet/organic semiconductor/ferromagnet magnetic tunneling junction and in ferromagnet/insulator/organic semiconductor/ferromagnet magnetic tunneling junction are investigated. The variation of tunneling magnetoresistance (TMR) with voltage and temperature are calculated. Furthermore, the dependence of TMR on the thickness of the insulator layer or organic semiconductor layer, and OSM/FM interfance potential barrier (U) were studied. The experimental observation reported recently can be well explained based on our calculations.