Thickness dependent magnetic properties of epitaxial La_0.7Sr_0.3MnO₃ thin films prepared by chemical solution deposition method

The correlation between films thickness and the physical properties (such as magnetic, magnetotransport properties) has been investigated in 5 nm and 160 nm La_0.7Sr_0.3MnO₃ (LSMO). The films were deposited on (100) SrTiO₃ (STO) substrates by chemical solution deposition method. High-resolution X-ray diffraction (HRXRD) and high-resolution transmission electron microscopy have been used to estimate the epitaxial structure and the change of strain. Both of the films are grown on STO substrates with coherent interfaces. The thinner sample has fully strained while the thicker film is partially strain relaxation. With decreasing film thickness from 160 to 5 nm, both of the T_C and T_MI strongly depressed. The strain and limitation of the spin fluctuations by the film thickness are the main origins of the Tc lowering. The MR value of S1 is much larger than that of S2 at 300 K. It can be elucidated by the existence of magnetic polarons around T_C and spin fluctuations in the interface between the film and the substrate.