Charge localization in nanometric La_(2/3)Ca_(1/3)MnO_(3) thin films grown on nearly matching substrates

摘要

By using magnetotransport measurements as well as nuclear magnetic resonance as local magnetic probe, we conclusively show that, irrespective of the film/substrate structural mismatch and film thickness, there are nonconductive regions at the film/substrate interface. We thus discard dimensional effects and structural mismatch as the main reasons for the suppression of conductivity and the weakening of the ferromagnetic coupling in nanometric thin films of manganites. We shall argue that this behavior is related to a charge localization which also leads to a weakening of the magnetic interactions and a decrease of the Curie temperature.