A strain-induced new phase diagram and unusually high Curie temperature in manganites

Raising the critical temperature of functional materials is a major challenge for the exploitation of many exciting physical phenomena, such as high- T c superconductivity, colossal magnetoresistance, and multiferroicity in strongly correlated systems. To this end, chemical doping, pressure, epitaxial strain, electric gating, interfacial charge transfer, and symmetry broken effects at the surface or edge have been used as the major means. While all these efforts have had some success, room temperature remains as the highly desirable yet difficult hurdle to clear. In this work, we demonstrate that the Curie temperature of a manganite system can be raised to over 300 K by tuning the epitaxial strain and chemical doping, and explain the underlying mechanism based on density functional theory (DFT) calculations and Monte Carlo (MC) simulations. Furthermore, we successfully designed a room temperature spin injector in a magnetic tunnel junction device based on the high- T c manganite.