Epitaxial growth and magnetoresistance of La1−xCaxMnO3−δ thin films on MgO(001) substrates

Perovskite La1−xCaxMnO3−δ thin films were deposited on MgO(001) substrates using pulsed laser deposition. Effects of deposition conditions, such as laser fluence, substrate temperature, and oxygen pressure, on growth behaviors of the films were investigated over a wide range. Epitaxial La0.7Ca0.3MnO3−δ /MgO thin films were able to be grown in situ under conditions such as 1.5–2.1 J/cm2 laser fluence, 650–750 °C substrate temperature, and 100–300 mTorr oxygen pressure. The oxygen pressure during the deposition is found to be closely related to crystalline orientations of the films. Rutherford backscattering spectroscopy measurements show that the epitaxial La1−xCaxMnO3−δ thin films have compositions similar to those of targets, demonstrating that pulsed laser deposition is a useful technique to get thin films with complicated chemical compositions. The magnetoresistance, −ΔR(6T)/R(0), of the La0.7Ca0.3MnO3−δ /MgO thin film was about −80%, which is smaller than the reported values (i.e., ∼−99.92%) of the La–Ca–Mn–O thin films on LaAlO3 substrates [S. Jin, T. H. Tiefel, M. McCormack, R. A. Fastnacht, R. Ramesh, and L. H. Chen, Science 264, 413 (1994)].