Mapping out the electronic and magnetic transitions in mixed-valent La_1-xSr_xMnO₃ thin films

The rich phase diagram in mixed-valent manganites has been intensely studied in bulk crystals as a function of chemical doping. Here we study the effect of doping in La_1-xSr_xMnO₃ thin films by varying the Sr/La ratio between samples. These thin films are grown using ozone assisted molecular beam epitaxy with carefully controlled stoichiometry for a range of doping from x = 0.0 to x = 0.5. Our electronic measurements reveal a crossover from a Mott insulator to a metallic ground state as x is increased. In the metallic ground state we observe a metal-to-insulator transition coincident with a ferromagnetic-to-paramagnetic ordering transition consistent with the double exchange interaction with higher, doping dependent transition temperatures compared to those reported for bulk La_1-xSr_xMnO₃ crystals. We will also discuss the magnetic ordering transitions observed in the low doping regime (x<0.17) where an insulating ground state is observed and compare these transitions with those reported for bulk La_1-xSr_xMnO₃ crystals.