Structural and ferroelectric properties of orthogonal crystalline in Fe-doped HoMnO3 synthesized at normal pressure

Abstract

A typical multiferroic manganese oxide of HoMnO₃ was partially substituted by Fe at Mn site. Orthogonal crystalline phase of HoMn_1−xFe_xO₃ was synthesized at normal pressure. This finding has changed the conventional method of synthesizing orthogonal crystalline phase of rare-earth manganese oxides under high-temperature and high-pressure. The doping of iron ions suppresses the formation of hexagonal phase as revealed from X-ray diffraction, Morphology analysis, Raman spectrum and X-ray photoelectron spectroscopy. The doping of Fe³⁺ into HoMnO₃ causes changes in the space group of the sample and ferroelectricity at room temperature. There are two phases with a ferroelectric space group of \[{P6}_{3}cm\] and a paraelectric one of Pnma coexisted in Ho\[{\text{Mn}}_{1-x}{Fe}_{x}{O}_{3}\] polycrystalline with x < 0.15 as revealed by the Rietveld refinement. With increasing of doping concentration, the proportion of \[{P6}_{3}cm\] gradually decreases. When x > 0.15, the phase with \[{P6}_{3}cm\] space group disappears, and samples have only one crystalline phase Pnma. We found that the sample remained ferroelectricity at room temperature in the process of changing the doping concentration. The ferroelectric property disappears until it completely changed to the orthogonal phase. The synthesis of orthogonal HoMnO₃ at normal pressure has not been previously reported and potentially open up abroad research and application prospects.