Unveiling the magnetic and optical properties of barium bismuthate thin films with distinct Ba/Bi ratios

ACERO, G.; PONCE, M.A.; MOURA, F.; SIMÕES, A.Z.

MATERIALS CHEMISTRY AND PHYSICS

ELSEVIER SCIENCE SA

Año: 2024 vol. 322

0254-0584

AbstractThis research aims to investigate the optical and magnetic properties of BaBiO3 (80:20), BaBiO3 (50:50), and BaBiO3 (30:70) thin films obtained by the polymeric precursor method. For better sample designations, the following codes were employed: (80:20) (BBO82), (50:50) (BBO55), and (30:70) (BBO37). The observed properties for barium bismuthates thin films were elucidated in terms of bismuth and oxygen vacancies as well as grain morphology, which can be controlled by stoichiometric changes (Ba/Bi ratios). According to the x-ray results the films crystallize in a rhombohedral BaBiO3 structure with an R-3R space group without any secondary phase as confirmed by Rietveld analyses. According to the photoluminescence results, x-ray photoelectron spectroscopy measurements as well as the law of approach to saturation (LAS), there are a significant presence of oxygen vacancies and vacancy clusters in the films with high proportion of bismuth. The optical and magnetic properties developed by these films are originated from the following factors: tilting of BiO6 clusters which changes the length and angle of Bi–O–Bi bonds, creating a magnetic field responsible for the distinct Mr/Ms ratios, the formation of bipolarons caused by charge transfer between [BiO6] and [BiO5. Vo⋅] due to the oxygen vacancies formation, plate-like morphology which makes the domains easier to be switched under an applied external field resulting in a superparamagnetic behavior, charge disproportionation of various valence states (Bi+3 and Bi+5). Based on these results, new potential devices can emerge as possible tools to be applied in switches, actuators, spintronics, magnetic field sensors, etc.