Anomaly of thermal properties in thin films of La_1-xSr_xCoO₃ series synthesized with a combinatorial processing

The thermal diffusivities throughout a composition-spread film comprising La_1-xSr_xCoO₃ series were determined by Transient Reflecting Grating (TRG) measurements. Thermal diffusivities of transparent SrCoO₃ film and SrTiO₃ substrate were determined by using third harmonics having wavelength of 266 nm as an excitation light with only a certain length of grating spacing. The thermal diffusivities of them were 0.02 and 0.05 cm²/s, respectively. With regard to untransparent thin films, the experiment was performed by setting three kinds of grating spacing for the excitation light having the fundamental wavelength, 800 nm in order to obtain high precision. The distribution profile of obtained values of the thermal diffusivity throughout the sample was traced as 0.06 - 0.18 - 0.01 cm²/s corresponding to the variation of χ in La_1-xSr_xCoO₃, thus showing a convex profile, however, this anomalous profile was verified by comparing with the data obtained by the X-ray diffractometer.