Correlation of microstructure and magnetotransport properties of epitaxially crown La2/3Ca1/3MnO3 thin films

Using the technique of pulsed laser deposition, we have studied the correlation of the film deposition conditions with the microstructure and magnetotransport properties of La-2/3 Ca1/3MnO3 thin films. Detailed TEM microstructure studies revealed the dependence of the local microstructure with the deposition temperature. The TEM studies reveal a distortion of the La2/3Ca1/3MnO3 lattice leading to a breakdown of the symmetry from orthorhombic to monoclinic. At high deposition temperatures (T < 800 degrees C), the substrate/film interface is perfectly coherent, suggesting that the film is strained due to the lattice mismatch. Effects of hydrostatic pressure on the resistivity of the films reveal an increase in temperature of the metal-insulator transition and a colossal change in resistivity qualitatively comparable to the magnetoresistance effect. The data are interpreted in terms of microstructure sensitive changes of the contraction and alignment of the Mn-O-Mn bonds.