The controlled generation of cationic vacancies in, keeping constant the concentration of electronic holes, was an unexplored way to suppress the charge-ordered state, leading to ferromagnetic and metallic materials with colossal magnetoresistance. The partial substitution of Ca by Sr in the cationic deficient manganites seems to be the key to get ferromagnetic and metallic conductor materials with colossal magnetoresistance at room temperature.

Room-Temperature CMR in Manganites with 50% Mn4+ by Generation of Cationic Vacancies. A.Arroyo, J.M.Alonso, R.Cortés-Gil, J.M.González-Calbet, A.Hernando, J.M.Rojo, M.Vallet-Regí: Journal of Magnetism and Magnetic Materials, 2004, 272-276[3], 1748-50