On the Anomalous Magnetic Behavior and the Multiferroic Properties in BiMn₂O₅

Sealed-tube synthesis of BiMn₂O₅ materials and their physical properties have rationally been reinvestigated depending on the reactants. The aim of the study was to characterize its potential multiferroic properties and to investigate the anomalous magnetic properties in relation to the expected ferroelectric properties. Rietveld refinement of the room temperature X-ray diffraction data shows the stability of the crystallographic structure with a Mn³⁺/Mn⁴⁺ ratio far from 1 because of bismuth and oxygen deficiencies despite the sealed-tube synthesis. Our detailed magnetic susceptibility and specific heat data analysis unambiguously support an intrinsic anomalous magnetic behavior in relation to the establishment of a magnetic short-range ordering far from the Néel temperature. Around room temperature, oxygen vacancies are responsible for supporting the dielectric loss peak measured, and, interestingly, the so-called <i>T</i>*, which was underlined in relation to an anomalous phonon shift (García-Flores, A. F.; et al. <i>Phys. Rev. B</i> <b>2006</b>, <i>73</i>, 104411), is not a characteristic temperature in relation to the multiferroic properties because no ferroelectric transition was detected