Large Magnetoresistance and Electrostatic Control of Magnetism in Ordered Mesoporous La_1–xCa_xMnO₃ Thin Films

Ferroic nanomaterials have received much attention in recent times because of their potential for novel applications. Here, we report a facile bottom–up synthetic approach to the first ordered mesoporous mixed-valence manganese oxide. Continuous thin films of perovskite-type La 0.68 Ca 0.30 Mn 1.02 O 3−δ have been prepared from common inorganic salt precursors by taking advantage of the superior templating properties of a polyisobutylene- block -poly(ethylene oxide) diblock copolymer. This novel solution-processed mesostructured material is well-defined at the nanometer and micrometer levels and behaves superparamagnetically above 230 K. Furthermore, it exhibits large magnetoresistance over a wide range of temperatures due to complex percolation pathways for electron transport imparted by the unique pore–solid architecture, and it is ferromagnetic metallic below 180 K. We also demonstrate reversible magnetization modulation of up to 8.5% by electrostatic charge carrier doping in the polymer-templated thin films. This value is the highest thus far reported for electrolyte-gated mixed-valence manganese oxides.