Preparations And Propetries Of Mixed-valence Manganites Films

Perovskite manganites belong to the strongly correlated system, and haveattracted much research interest both in physical properties and practical applications.La_0.85K_0.15MnO₃LKMO)，which is of perovskite structure, with the two kinds ofions whose oxidation states difference is two, has been synthesized by solid statereaction. Its nominal composition and crystal structure have been determined by ICPand XRD, respectively. We prepared the LKMO crystals into thin films using PLDapproach. The partial erosion, X-ray reflectivity （XRR） and cross-sectional SEMmethods have been applied to determine the thicknesses of the films, and their resultsdifference has been analyzed. The crystal qualities of the films were studied usingXRDωscans. Then the effects of Oxygen pressure and substrate temperature on theroughness of the films were studied. Meanwhile, thin films of Sr0.5Ce0.5MnO3werealso deposited with PLD and the oxidation states of Mn were analyzed using XPS.Since the Curie temperature and GMR effect are two important parameters for theGMR materials, we investigate the effect of thickness on the Curie temperature, andinterpreted the effect in the terms of orbital order and Mn-O-Mn angle. We alsoinvestigated the light absorption and emission properties of LKMO, and compared theproperties with those of other perovskite manganites. In the last part, unepitaxialtrilayer films with p/i/n structure were prepared and their transport properties werestudied under ac field, a rectifying effect can be observed in the relatively highvoltage.