Metal-insulator transition above room temperature in maximum colossal magnetoresistance manganite thin films

It has been suggested that the maximum magnitude of colossal magnetoresistance occurs in mixed-valent manganites with a tolerance factor t=0.96 [Zhou, Archibald, and Goodenough, Nature (London) 381, 770 (1996)]. However, at t approximate to 0.96 most manganites have relatively low values of the metal-insulator transition temperature T-MI (similar to 60-150 K). Here, we report that a 50 A La0.9Sr0.1MnO3 thin film with t=0.96 grown on a (100) SrTiO3 substrate has a metal-insulator transition above room temperature, which represents a doubling of T-MI compared with its value in the bulk material. We show that this spectacular increase of T-MI is a result of the epitaxially compressive strain-induced reduction of the Jahn-Teller distortion.