Correlation of microstructure and magnetotransport properties of epitaxially grown La-Ca-Mn-O_3 thin films

摘要

We have investigated structural, transport and optical properties of epitaxially grown single-crystalline Ca - doped LaMnO_3 thin films prepared by the pulsed laser deposition technique. This is a case study aimed to explore the possibilities buried in epitaxial stress tailoring in order to control the transport properties of CMR materials beyond the limits set by equilibrium thermodynamics for bulk materials. Depending on the film thickness there is an abrupt transition from pseudomorphic to epitaxial granular growth observable which is related to the epitaxial strain of the films. The abrupt transition is associated with microscopic stress relaxation and leads to well controllable modifications of the atomic arrangement of the Mn-O sublattice in the films. Due to the interrelation of double exchange, spin-, charge- and orbital ordering and the Jahn-Teller effect mediated coupling of the electronic system to the crystal lattice, the magnetotransport properties of the films can be modified in a controllable way.