Synergistic effects of hydrogenation and a noble metal on the topotactic and magnetic modulations of manganite films

The search for high-temperature ferromagnetic insulators is crucially important for low-power spintronic storage devices. However, very few ferromagnetic insulating materials with a Curie temperature above 300 K have been reported to date, which greatly hinders their practical applications. Here, using a hydrogen plasma reduction method, we modulated the topotactic structure, resultant magnetism, and electrical insulation in La_0.7Sr_0.3MnO_3 films constrained by different misfit strains. We observed an ultrafast structural transformation from the pristine La_0.7Sr_0.3MnO_3 perovskite state to the hydrogenated brownmillerite La_0.7Sr_0.3MnO_2.5 state as a function of the bias voltage of a low-frequency inductively coupled plasma system. Meanwhile, Pt electrodes capped on the film surfaces further promote the stabilization of the hydrogenated brownmillerite La_0.7Sr_0.3MnO_2.5, accompanied by enhanced magnetic insulation for temperatures up to 400 K. Such subtle engineering of functional perovskite-derived oxide films offers insights into the development of emergent materials for promising spin-polarized tunneling devices.