Implications of magnetic dilution of PrFeO3 with Bi3+ on its dielectric and magnetic properties

Abstract

Research on functional oxide ceramics has tremendous translational potential for technological applications. Despite sharing a similar formula, BiFeO₃ and REFeO₃ (RE = rare earth) perovskites differ widely in structure and properties. The potential of substituting non-magnetic Bi³⁺ with a stereochemically active 6s² lone pair in rare-earth ferrites remains largely unexplored. In this work, the consequences of replacing Pr³⁺ with Bi³⁺ on the dielectric and magnetic properties of PrFeO₃ were investigated by synthesizing the samples using a solution combustion method. The inclusion of bismuth led to local site disorder and promoted the reduction of more amounts of Fe³⁺ to Fe²⁺, as verified by Raman and XPS measurements. The higher concentration of Fe²⁺ resulted in the formation of oxygen vacancies. The band gaps of the pure and Bi-substituted PrFeO₃ samples were in the range of 1.90–2.08 eV. The field and temperature-dependent magnetic measurements of Pr_1−xBi_xFeO₃ confirmed the magnetic dilution. ZFC and FC measurements at low fields revealed a spin reorientation transition at 101 K in the case of Pr_0.70Bi_0.30FeO₃, which supported the negative exchange bias effect at room temperature. The dielectric constant increased with an increase in bismuth content. Electronic structure calculations with charge density plots revealed the induction of polarization by the electric field in the Bi³⁺-containing samples. This was also verified through PUND measurements, which showed the existence of intrinsic and switchable polarization (0.17 μC cm⁻²). The random distribution of the stereochemically active 6s² lone pair on Bi³⁺ has been proposed as the reason for the observed polarization.