Preparation Of LSMO/PANI(DBSA Doped)/Co/Pt Organic Spin Valve And Study On The MR Effect

The spin valve uses electron spin instead of the traditional nature of electron charge; it is highly sensitive in magnetic response, non-volatile, and has high storage density, which are widely used in high technologies. In this thesis, organic semiconductor DBSA doped polyaniline are chosen as the middle layer. The completely organic spin valve La_0.67Sr_0.33MnO₃ / Polyaniline (DBSA doped) / Co / Pt was successfully prepared, and its magnetoresistance(MR) effects were studied.First, the preparation of LSMO film,DBSA doped PANI film, Co film and Pt film were discussed. For each layer of films, the structure, magnetic properties, electrical transport properties were tested and analysized, and to ensure that the performance of each film is meets the requirements of spin valve.Second, after the device fabrication is completed, the morphorlogy and the structure of the film cross section was observed with a field emission scanning electron microscope to analyse the multilayer structure and to insure failure layer had been produced. This study showed spin valve was fabricated in decent sturcture, and further electrical transport properties were studied.Finally, the focus was the testing and analysis of the R-H curves of spin valves. It was found that the MR effect of spin valve increased with decreasing middle layer thickness, and the spin diffusion length of PANI at below 82K was estimated. Further more, the impact of varying temperature on the spin valve MR effect was studied, and found that it decreased with increasing temperature, and finally disappeared. This phenomenon was also related to the of influence of the spin diffusion length of the middle organic layer, which decreased when temperature got high. Througth tests and analyses, the significant influence of the intermediate organic layer on the MR effect of spin valve was demostrated.