Pathways to obtain high-entropy BiFeO3-based thin films modified by rare earth cations

Abstract

Bismuth ferrite (BiFeO3) is a prototypical multiferroic material with coexisting ferroelectric and magnetic orders, and is considered promising for next-generation electronic devices. However, challenges that remain to be overcome limit its commercial application and stimulate the research. This work reports a study replacing the Bi site with multiple rare earth elements for the synthesis of Math input error thin films at compositions 0.00 ≤ x ≤ 0.20 to explore possible new properties based on the evolution of their structural, ferroelectric, dielectric, and magnetic properties. With increasing the substitution of rare-earth cations, the room-temperature magnetization increases, whereas the dielectric permittivity and electrical conductivity decrease. Concurrently, the crystalline structure evolves from the rhombohedral phase (space group R3c) in pure BiFeO3 to a predominantly orthorhombic phase (space group Pbnm), coexisting with residual traces of a rhombohedral phase in the high-entropy composition (Math input error). Remarkably, ferroelectricity is retained in films with Bi content as low as 60 mol% (Math input error), while in high-entropy composition, the observed local hysteresis loops and the contrasts in PFM amplitude and phase images suggest the presence of a possible improper ferroelectric state, which must be confirmed or refuted through further experiments.