Giant Magnetoresistance Effects In LSMO/PANI/Co Spin Valve Device

Spintronics is a relatively new and promising field, which could achieve the practical application of the electron-spin through spin polarization and spin transportation with the manipulation of electron-spin. Spintronics is widely used for its high magnetic sensitivity, high storage density and non-volatility in the fields of magnetoresistance sensors, read heads and magnetic recording. Due to very weak spin-orbit interaction in organic semiconductors, the spin polarization of carriers can maintain for a long time, organic semiconductors are paid much attention for the potential applications in spintronics.Organic spin valve is a fundermental device which could achieve the utilization of organic semiconductors in spintronics. This article is focus on the study of the factors that could affect magnetoresistance. Using La_0.67Sr_0.33MnO₃ (LSMO) as the bottom electrode, doped polyaniline (PANI) or 8-hydroxy-quinoline aluminium (Alq₃) as interlayer and cobalt (Co) as top electrode, we succeed in the preparation of the spin valves LSMO/PANI/Co and LSMO/Alq₃/Co, and achieve a magnetoresistance of 54% at T=80K and I=+0.1mA. It is found that the relationship between magnetoresistance and temperature in organic spin valve is governed by the ferromagnetic electrodes, independent of organic interlayer. It is predicted that sizable MR effects may be achieved in room temperature in organic spin valve while substituting LSMO electrode with temperature independent FM electrodes.This article is divided into four chapters, and as follows:Chapterâ… : A brief overview of the research progress and problems of organic spin valves; A brief summary of the purpose of this article.Chapterâ…¡: Description of the preparation and properties of LSMO, Co, PANI and Alq₃. Chapterâ…¢: Description of the preparation of spin valves; Study on the structure and electric transportation of spin valves and try to explore the factors that could affect magnetoresistance. It has been found that the LSMO ferromagnetic electrodes dominate the magnetoresistance decrease with temperature. Ferromagnetic electrodes with milder temperature dependence are needed in order to achieve sizable magnetoresistance values at room temperature.Chapterâ…£: Conclusions and outlook about this article.