La1-xCaxMnO3外延薄膜的制备、结构及磁电阻效应

采用溶胶-凝胶旋涂法在单晶LaAlO3 (100)基片上生长了La1-xCaxMnO3(x=0, 0.05, 0.1, 0.2)外延薄膜. 利用X射线衍射仪(XRD)、 原子力显微镜(AFM)、 聚焦离子束系统(FIB)、 X射线光电子能谱分析仪(XPS)、 振动样品磁强计(VSM)和磁性测量系统(MPMS)对样品的结构、 形貌、 价态、 居里温度和磁电阻效应进行了研究. 结果表明, 薄膜为立方钙钛矿结构, 具有明显的(100)外延生长取向和平整的表面. 在居里温度附近, 样品发生铁磁-顺磁转变. 随着Ca2+掺杂量的增加, 样品的居里温度升高, La0.8Ca0.2MnO3的居里温度为264 K. 随温度的变化, 样品发生了金属-绝缘体转变. 样品还具有较大的磁电阻效应, 在H=2.0 T, T=210 K时, La0.95Ca0.05MnO3的磁电阻达到80.9%.

Preparation, Structure and Magnetoresistance Effect of La1-xCaxMnO3 Epitaxial Film

La1-xCaxMnO3(x=0, 0.05, 0.1, 0.2) epitaxial films were grown on LaAlO3 (100) single-crystal substrate by sol-gel spin-coating method. The crystal structure, morphology, valence state, curie temperature and magnetoresistance effect of the films were investigated via X-ray diffractometer, atom force microscope, focused ion beam system, X-ray photoelectron spectrometer, vibrating sample magnetometer and superconduc-ting quantum interference device. The results show that the crystal structure of the film is cubic with high (h00)-oriented epitaxial direction and smooth surface. The maximum of Curie temperature is 264 K. Near the Curie temperature, the magnetic properties exhibit a transition from ferromagnetism to paramagnetism. The La0.95Ca0.05MnO3 film exhibit a maximum magnetoresistance ratio of 80.9% at 210 K and 2.0 T magnetic field.