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 correla tion of the film deposition conditions with the microstructure and magnetot ransport properties of La-2/3 Ca1/3MnO3 thin films. Detailed TEM microstruc ture studies revealed the dependence of the local microstructure with the d eposition temperature. The TEM studies reveal a distortion of the La2/3Ca1/ 3MnO3 lattice leading to a breakdown of the symmetry from orthorhombic to m onoclinic. At high deposition temperatures (T < 800 degrees C), the substra te/film interface is perfectly coherent, suggesting that the film is strain ed due to the lattice mismatch. Effects of hydrostatic pressure on the resi stivity of the films reveal an increase in temperature of the metal-insulat or transition and a colossal change in resistivity qualitatively comparable to the magnetoresistance effect. The data are interpreted in terms of micr ostructure sensitive changes of the contraction and alignment of the Mn-O-M n bonds.