We report magnetic and transport properties of ${\mathrm{La}}_{1-x}{\mathrm{Ba}}_x{\mathrm{MnO}}_3$ $(x=0.05\mathrm{}–0.33)$ epitaxial thin films. Compared with the corresponding bulk materials, the ferromagnetic transition temperature is reduced in the compressive strained ${\mathrm{La}}_{1-x}{\mathrm{Ba}}_x{\mathrm{MnO}}_3$ thin films with $x=0.3\mathrm{}$ and 0.33, but enhanced significantly in the tensile strained thin films with $x<~\mathrm{0.2.}$ Especially, ferromagnetism and low field colossal magnetoresistance effect were observed around room temperature in $x=0.1\mathrm{}$ thin film, and as $x=0.05,$ a spin-canting insulating state in bulk shifts to ferromagnetic metallic state in thin film. The phase diagram of ${\mathrm{La}}_{1-x}{\mathrm{Ba}}_x{\mathrm{MnO}}_3$ thin films was obtained, and strain effect on these novel properties was discussed.

• Received 16 April 2001

DOI:https://doi.org/10.1103/PhysRevB.64.184404