La_(1-x)Ca_xMnO_3外延薄膜的制备、结构及磁电阻效应

Preparation,Structure and Magnetoresistance Effect of La_(1-x)Ca_xMnO_3 Epitaxial Film

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%.

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.