Epitaxial strain induced metal insulator transition in La0.9Sr0.1MnO3 and La0.88Sr0.1MnO3 thin films

We are reporting an unexpected metal insulator transition at the ferromagne tic phase-transition temperature for thin films of La0.9Sr0.1MnO3 (< 50 nm) , grown on a (100) face of SrTiO3 substrate. For the thicker films (> 50 nm ), similar to the single crystal, no such transition is observed below T-C. Additionally, we observe the suppression of the features associated with c harge or orbital ordering in intentionally La-deficient thin films of La0.8 8Sr0.1MnO3 (< 75 nm). In thin films, transmission electron microscopy revea ls a compressive strain due to the epitaxial growth, that is, lattice param eters adopt those of the cubic lattice of SrTiO3. As the film thickness inc reases, coherent microtwinning is observed in the films and the films relax to a orthorhombic structure. (C) 2000 American Institute of Physics. [S000 3-6951(00)00402-2].