The Lanthanum manganite perovskites are some of the most captivating magnetic materials due to their colossal magnetoresistance (CMR), half-metallicity, magnetocaloric, and optical properties. Among these manganites, the La0.7Sr0.3MnO3 (LSMO) has the highest Curie temperature of 369 K, the large saturation magnetization and a Curie temperature above room temperature have the potential for use in hyperthermia, magnetic resonance imaging contrast enhancement, drug delivery, magnetic tunnel junctions, hot-electron based transistors, and ferroelectric tunnel junctions. The rich phase diagram of LSMO and the strong coupling between the magnetic and electronic phases in thin LSMO films stacked on different substrates such as SrTiO3, NdGaO3, DyScO3, LaAlO3 (LAO), MgO, (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7, and Si have been widely investigated. In the thesis, the effect of interfacial reconstruction in a series of LSMO films grown on (001) oriented LAO and Si substrates using the pulsed plasma sputtering technique is demonstrated. The interfacial reconstruction occurs at the LSMO–LAO interface because of the Mn ion spin’s reorientation, which induces spin-glass behavior and non-collinear orientations of Mn ion spins. Consequently, the interface effect was observed on the Curie temperature, temperature-dependent resistivity, metal-to-semiconductor transition temperature, and magnetoresistance (MR). At a magnetic field of 7 T, the MR decreased from 99.8 % to 7.69 % as the LSMO film thickness increased from 200 A to 500 A. A unique characteristic of these LSMO films is the occurance of large low-field MR after a decrease in the field from the maximum field 7 T (Nanoscale Adv., 2, 2792-279 (2020)). The LSMO films gown on (001) Si exhibit positive MR, although the bulk LSMO is well known for colossal negative MR. The positive MR is explained by the interfacially localized and antiferromagnetically coupled non-collinear spins. The first principle density functional theory calculations confirm the occurrence of charge transfer from the Si to LSMO film, which triggers the orbital re-hybridization in the MnO6, i.e., the low magnetic moment of the Mn ions. The magnetic anisotropy (MA) established in a 95 Å thick film of LSMO is ~1.07×106