Substrate induced strain effects in epitaxial La0.67−xPrxCa0.33MnO3 thin films

We have studied the physical properties of epitaxial La0.67−xPrxCa0.33MnO3(LPCMO) (x=0.13, 0.20, 0.27) thin films under different type and degree of substrate induced biaxial strain. Films with thickness of 300, 600, and 1000 A grown on crystalline NdGaO3 (negligible strain), LaAlO3 (compressive strain), and SrTiO3 (tensile strain) by pulsed laser deposition are examined. Our data suggest occurrence of metastable phase mixtures in these films, with the volume fractions controlled by strain. In particular, melting of the charge ordered phase is seen to occur in thin films on SrTiO3 at fields as low as 1 T, in the low temperature regime. The deviation of ρ(T) from the effective medium theory further indicates that LPCMO thin films cannot be described as simple metal–insulator mixtures.