Strain effects on the ferromagnetic and electronic properties in (La _0.91,Sr_0.09)MnO₃ thin films

La1-x Srx Mn O3 (LSMO) thin films with a polycrystalline structure of variable thickness were deposited by a radio-frequency magnetron sputtering system on Si O2 (200 nm) Si (100) substrate. The ferromagnetic property and electrical transport increased with increasing film thickness. This can be considered as the result of small deformation of the Mn-O bond length/bond angle due to the relaxation of tensile strain, which enhances the ferromagnetotransport properties. Additionally, there is an oxide layer found at the interface between the film and substrate from the transmission electron microscopy observation. It is also exhibited by conductive atomic force microscopy measurement that the metallic and insulative regions are coexisted in all of the films.