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

Abstract

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 $t\ensuremath{\approx}0.96$ most manganites have relatively low values of the metal-insulator transition temperature ${T}_{MI}\phantom{\rule{0.3em}{0ex}}(\ensuremath{\sim}60\text{--}150\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. Here, we report that a 50 \AA{} ${\mathrm{La}}_{0.9}{\mathrm{Sr}}_{0.1}{\mathrm{MnO}}_{3}$ thin film with $t=0.96$ grown on a (100) ${\mathrm{SrTiO}}_{3}$ 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.