Evolution of electrical and magnetotransport properties with lattice strain in La_0.7Sr_0.3MnO₃ film

In this paper, we investigate the effects of lattice strain on the electrical and magnetotransport properties of La_0.7Sr_0.3MnO₃ (LSMO) films by changing film thickness and substrate. For electrical properties, a resistivity upturn emerges in LSMO films, i.e., LSMO/STO and LSMO/LSAT with small lattice strain at a low temperature, which originates from the weak localization effect. Increasing film thickness weakens the weak localization effect, resulting in the disappearance of resistivity upturn. While in LSMO films with a large lattice strain (i.e., LSMO/LAO), an unexpected semiconductor behavior is observed due to the linear defects. For magnetotransport properties, an anomalous in-plane magnetoresistance peak (pMR) occurs at low temperatures in LSMO films with small lattice strain, which is caused by two-dimensional electron gas (2DEG). Increasing film thickness suppresses the 2DEG, which weakens the pMR. Besides, it is found that the film orientation has no influence on the formation of 2DEG. While in LSMO/LAO films, the 2DEG cannot form due to the existence of linear defects. This work can provide an efficient way to regulate the film transport properties.