TEM characterization of CMR thin film on [001] SrTiO3 substrate
Due to its potential magnetic device application, giant/colossal magnetoresistant (GMR or CMR) material, (bulk material as well as thin film), have been under intense investigation in recent years. In the bulk material, the changes of the resistivity under 4T magnetic field is about 80% at the metal-insulate transition temperature for La0.7Ca0.3MnO3 (LCMO). In 1994, S. Jin et al reported thousandfold change in resistivity in magnetoresistive La-Ca-Mn-0 films on a LaAlO3 substrate. It is suspected that such a large magnetoresistivity change in the thin film is due to the defect structure in the epitaxially grown thin film.The base structure of LCMO is an MnO6 octahedral perovskite cubic structure. Because of its strong static Jahn-Teller (JT) distortion, the compound is metrically orthorhombic, with a∼b∼√2 ap and c∼2ap where ap is the lattice constant for the base cubic structure. X-ray diffraction study on this compound shows that it belongs to Pnma space group.