Response of the electrical resistivity and magnetoresistance of La 0.67Ca0.33MnO3 Films to Biaxial Tensile Strains

The structure, electrical resistivity, and magnetoresistance of (50-nm)La"0"."6"7Ca"0"."3"3MnO"3 epitaxial films grown on a [(80m)Ba"0"."2"5Sr"0". "7"5TiO"3/ La"0"."3Sr"0". "7Al"0"."6"5 Ta"0"."3"5O"3] substrate with a substantial positive lattice misfit have been studied. The tensile biaxial strains are shown to account for the increase in the cell volume and in the relative concentration of Mn(+3) ions in the manganite films as compared to those for the original material (33%). The peak in the temperature dependence of the resistivity ρ of La"0". "6"7Ca"0"."3"3MnO"3 films was shifted by 30-35 K toward lower temperatures relative to its position in the ρ(T) graph for a manganite film grown on (001)La"0"."3Sr"0". "7Al"0"."6"5Ta"0"3"5O"3. For T < 150 K, the temperature dependences of ρ of La"0". "6"7Ca"0"."3"3MnO"3/Ba"0". "2"5Sr"0"."7"5TiO"3/La"0". "3Sr(0.7) Al"0"."6"5Ta"0". "3"5O"3 films could be well fitted by the relation ρ = ρ"0 + ρ"1T4.5, where ρ"0 = 0.35 mΩ cm and the coefficient ρ"1 decreases linearly with increasing magnetic field. In the temperature interval 4.2-300 K, the magnetoresistance of manganite films was within the interval 15-95% (μ"0H = 5 T)