在蓝宝石衬底上生长的La_0.5Ca_0.5MnO₃薄膜的面内取向问题研究

【作者】 许佳；

【导师】 谭伟石；

【作者基本信息】 南京理工大学 ， 凝聚态物理， 2010， 硕士

【摘要】 自从在La2/3Ca1/3MnO3外延薄膜中发现庞磁电阻效应以来,钙钛矿型锰氧化物R1-xAxMnO3(R=La,Nd,Sm,Pr;A=Ca,Sr,Ba,Pb等)一直倍受人们的关注。钙钛矿型锰氧化物在铁磁居里温度附近表现出较大的磁电阻效应(在几特斯拉磁场下可达106%)。与块材相比,锰氧化物薄膜表现出较大的磁电阻效应。锰氧化物薄膜的微结构受到衬底性质的影响,而锰氧化物薄膜的微结构决定了它的磁性和输运性质。因此,对薄膜结构的研究有助于加深对类钙钛矿锰氧化物所具有的各种奇特物性的理解,也会推动以此类材料为基础的磁电子器件的研制。过去在蓝宝石衬底上生长的锰氧化物薄膜大多是多晶的。本文使用传统固相反应法制作La0.5Ca0.5MnO3靶材,然后通过脉冲激光沉积法在(0001)取向的蓝宝石衬底上生长了La0.5Ca0.5MnO3薄膜。通过调整薄膜制备条件,得到了具有取向性的薄膜。论文利用常规X射线衍射方法分析了La0.5Ca0.5MnO3薄膜与A12O3衬底之间的面外取向关系,然后利用X射线掠入射衍射方法分析了薄膜与衬底的面内取向关系,最终得到薄膜与衬底之间存在着三组平行关系：(110)f//(0006)s,((?))f//(3030)s,(112)f//(1210)s。但是由于X射线衍射技术的局限性,还需借助其他实验技术进一步确认得到的面内取向关系。实验所得到的数据中也存在着一些暂时无法解释的现象,还需做进一步研究。更多还原

【Abstract】 Perovskite manganites with the formula R1-xAxMnO3 (R=La, Nd, Sm, Pr; A=Ca, Sr, Ba, Pb) have renewed interest since the colossal magnetoresistance was discovered in the epitaxial film. Perovskite manganites display the bigger magnetoresistive effect nearby the ferromagnetic Curie temperature(reach 106% under several Tesla magnetic field). Compare with the bulk materials, manganite films exhibit a stronger magnetoresistive effect. The microstructure of manganite films rely on the nature of substrate, moreover, the microstructure of manganite films influences strongly its magnetism and the transport property. Therefore, the study of the structure of the film will be helpful to understand a variety of peculiar properties in the perovskite-like manganites, and promote the development of magnetoelectronic devices based on such materials.In the past, all the reports on the growth of manganite films on the sapphire substrate have indicated that the films are polycrystalline in nature. In this article we used the traditional solid state reaction to manufacture La0.5Ca0.5MnO3 target, then we grew the La0.5Ca0.5MnO3 film through the pulse laser deposition on the (0001) orientation sapphire substrate. Through the adjustment of the experiment condition, we obtained the oriented film. In the article we used the conventional X-ray diffraction method to analyze the out-of-plane orientation relationship between the La0.5Ca0.5MnO3 film and Al2O3 substrate and the glancing incidence X-ray diffraction to analyze the in-plane orientation relationship between the film and the substrate, Finally we discovered three groups of parallel relationship between the film and the substrate:(110)f//(0006)s, (220)f//(3030)s, (112)f //(1210)s. But as a result of the X-ray diffraction technical limitation, we need to confirm the obtained in-plane orientation relationship by other experiment technology. In the experiment we also obtained the phenomena which are unable to be explained temporarily and need further studies.更多还原