Magnetic, optical, and photoelectrochemical properties of Er0.75Y0.25Fe1-xCoxO3 (x = 0.05, 0.15, 0.3, and 0.5): a Mössbauer and X-ray photoelectron spectroscopy study.

Polycrystalline Er0.75Y0.25Fe1-xCoxO3 (x = 0.05, 0.15, 0.3, and 0.5) perovskites were synthesized via the solid-state reaction method, and their structural, magnetic, optical and photoelectrochemical properties were investigated. Rietveld refinement of powder X-ray diffraction data confirmed an orthorhombic perovskite phase (Pbnm) for all compositions. Magnetic studies demonstrated weak ferromagnetism governed by the interplay of Dzyaloshinskii-Moriya (DM) and superexchange interactions. Spin reorientation transitions TSR exhibited as broad temperature intervals moved to higher temperatures relative to pure ErFeO3, ranging from 104-174 K (x = 0.05), 125-178 K (x = 0.15), 228-340 K (x = 0.3), and 133-233 K (x = 0.5). X-ray photoelectron spectroscopy revealed mixed Co3+/Co4+ states along with oxygen non-stoichiometry, consistent with Mössbauer evidence of weakened Fe-O-Fe exchange interactions. Mott-Schottky measurements indicated a decrease in valence band potential (from 3.51 to 3.07 eV) along with a transition from p-n to p-type semiconducting behaviour. These results highlight a tunable system with coupled spin, structural, and electronic functionalities, making it a promising candidate for spintronic and photoelectrochemical applications.