Ferromagnetism and metal-insulator transition in F-doped LaMnO3

We present our studies on polycrystalline samples of fluorine doped ${\mathrm{LaMnO}}_{3}$ (${\mathrm{LaMnO}}_{3\ensuremath{-}y}{\mathrm{F}}_{y}$). ${\mathrm{LaMnO}}_{3\ensuremath{-}y}{\mathrm{F}}_{y}$ exhibits remarkable magnetic and electrical properties. It shows ferromagnetic and metallic behavior with a high Curie temperature of $\ensuremath{\approx}239$ K and a high magnetoresistance of $\ensuremath{-}64%$. This drastic change in magnetic properties in comparison to pure ${\mathrm{LaMnO}}_{3}$ is ascribed to the presence of mixed-valence Mn ions driven by the F-doping at the O-sites, which enables double exchange in ${\mathrm{LaMnO}}_{3\ensuremath{-}y}{\mathrm{F}}_{y}$. Furthermore, the resistivity data exhibits two peaks at 239 and 213 K, respectively. Our results point towards the possibility of multiple double exchange hopping paths of two distinct resistances existing simultaneously in the sample below 213 K.