X-ray diffraction study of mixed-phase BiFeO3: Structural modulation via proton injection

Incorporating hydrogen into transition metal oxides with intricate structures offers significant potential for discovering exotic phenomena and functionalities by facilitating interactions between hydrogen ions and structural phases. Mixed-phase (MC + R′/T′ phases) BiFeO3 (BFO) has attracted considerable attention due to its numerous physical property discoveries, making it a promising candidate for modulation through hydrogen insertion. This study systematically investigates the structural evolution of BFO films under three distinct hydrogen injection methods: noble metal-catalyzed injection, ionic liquid gating, and hydrogen reduction. Comprehensive XRD analysis reveals that varying proton pathways and injection intensities induce characteristic structural modifications. X-ray absorption spectroscopy and x-ray photon spectroscopy results provide a more in-depth examination of the variations in valence states and oxygen ions migration induced by protonation in BFO films. Furthermore, the magnetism of the mixed-phase BFO increases, and the spontaneous polarization domains are enhanced, during the migration of protons and oxygen ions. This work provides valuable insights into hydrogen-associated electronic phase transitions within the mixed-phase BFO, advancing its potential applications in next-generation electronic devices.