Strain Effect And Field Modification In Epitaxial Thin Films Of Perovskite Manganite

Perovskite manganite have received a great deal of interest in physics and material science because of a variety of interesting properties such as colossal magnetoresistance(CMR), charge/orbital ordering, phase separation, Mott transition and so on. The preovksite manganites are at the quantum phase boundary and their novel behaviors are associated with the coexistence and competition of quantum states, which are sensitive to the external fields including magnetic field, electrical field, light and strain. In this dissertation, La0.7Sr0.3Mn O3(LSMO)films are chosen to study their photoconductivity, electrical property, magnetical property under strain. The main contents and research results are concluded as follows:1. High-quality epitaxial LSMO films have been grown directly on La Al O3(LAO)(001) substrate by pulsed laser deposition using optimized the deposition conditions.2. The electric-magnetic transport properties and photoinduced effect have been studied. The metal-insulator transition was not observed at temperatures from 50 K to 400 K and transition temperature(T c) was very high in LSMO/LAO thin films. Negative magnetoresistance and positive photoconductivity were found in the films.3. High-quality LSMO films have been grown on Sr Ti O3(STO),(La, Sr)(Al, Ta)O3(LSAT) and La Al O3(LAO) substrates. The electric-magnetic transport and photoconductivity under strain have been investigated. The strain effect can induce the decrease of T c and have great influence on electric-magnetic transport properties.