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In this paper, we illustrate an approach to discriminate between\ud epitaxial strain and other factors responsible for the decrease of the\ud metal-insulator transition temperature (T-P) in thin La0.7Sr0.3MnO3\ud films grown by pulsed laser deposition. Using this approach, we have\ud estimated the effect of the biaxial strain on T-P. Ultrathin films,\ud independent of epitaxial strain, do not show any metal-insulator\ud transition over the full temperature range. This finding confirms the\ud existence of an interface dead layer. The strain-independent decrease in\ud T-P, relative to its bulk value, observed for a much wider thickness\ud range (up to about 1000 A) can most likely be attributed to oxygen\ud deficiency. (C) 2004 American Institute of Physics

We have grown LaMnO3 thin films on (001) LaAlO3 substrates by pulsed\ud laser deposition. X-ray diffraction confirms that the films are only\ud slightly relaxed and are oriented ``square on square{'' relative to the\ud substrate. The measured Raman spectra closely resemble that observed in\ud bulk LaMnO3, which indicates no relevant distortions of the MnO6\ud octahedra induced by the epitaxial strain. Therefore, no detectable\ud changes in the lattice dynamics occurred in our LaMnO3 strained films\ud relative to the bulk case. Mn-55 nuclear magnetic resonance identifies\ud the presence of localized Mn4+ states. Superconducting quantum\ud interference device magnetization measures T-N=131(3) K and a saturation\ud moment mu=1.09 mu(B)/Mn, revealing a small concentration of Mn4+ and\ud placing our films within the antiferromagnetic insulating phase. (c)\ud 2006 American Institute of Physics.

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