Influence of the stress on the transport behavior of La_0.83Sr_0.17MnO₃ film

The LSMO (x = 0.17) film on the Si(111) substrate was fabricated by the sol-gel method. The R-T curves, the infrared spectra and XRD results of the block and the film with different thickness show that the crystals of the LSMO films are orthogonal, and the film orientation has some relation with the film thickness. When the film thickness lies between the 450 nm to 680 nm, the orientation is <200>, but when the film thickness equals to 900 nm, the orientation is <020>. According to the reactive energy and the harmonic oscillator model, the relational expressions, between the infrared absorption and the Mn-O-Mn bond length and bond angel were studied. The infrared absorption near 600 cm^-1 relates to the different lattice constant b, and the metal-insulator transformation temperatures (T_MI) of the block material and the films differ much, those of the films being much lower than that of the block material and, at the same time, has something to do with the film thickness. The paper indicates that the stress in the LSMO films inducing the lattice constant change and then arousing the change of bond angel and JT effect is the main reason for the change of the transformation temperature.