X-ray Diffraction Study Of Doped Rare Earth Manganese Oxide Thin-film Micro-strain

Colossal magnetoresistance (CMR) has been found near the Curie temperature and insulator(semiconductor)-metal transition temperature in carrier-doped perovskite manganites. It has attracted much recent attention because of the importance of its technological applications in magnetic recording and sensor, and of the effects of the electronic strong correlation in the field of basic study. We are convinced that the comprehension of complex problems posed by the manganites has the potential to produce a substantial advance in the theory of condensed matter physics.Bulk manganites La_0.7Ca_0.3MnO (LCMO) and La_0.8Ba_0.2MnO₃ (LBMO) were prepared by standard solid reaction technique. The lattice parameters of these two bulk samples were analysed with Rietveld refinement of powder X-ray diffraction pattern. La_0.7Ca_0.3MnO₃ thin films with the thickness of 200A,500A,1000A, and La_0.8Ba_0.2MnO₃ thin films with the thickness of 100A,200A,500A,1000A, were deposited on (001)-oriented single crystal Yttrium-stablized ZrO₂(YSZ) substrate with 90° off-axis radio frequency magnetron sputtering. Grazing incidence X-ray diffraction technique, associated with normal X-ray diffraction, was applied to measure the in-plane lattice parameter and investigate the lattice strain and strain relaxation in La_0.7Ca_0.3MnO₃, La_0.8Ba_0.2MnO₃ films. The results indicated that, for LCMO/YSZ film, the in-plane lattice parameters in films decrease with distance apart from the film/substrate interface. The mechanism for strain relaxation in LCMO/YSZ system with large lattice mismatch may be different from that for system with small lattice mismatch, such as tetragonal distortion. Furthermore, the strain in LCMO/YSZ and LBMO/YSZ film is nonuniform.