We report on the discovery of an isothermal structural transition observed in Bi${}_{1-x}$La${}_x$FeO${}_3$ ($0.17⩽x⩽0.19$) ceramics. At room temperature, an initially pure polar rhombohedral phase gradually transforms into a pure antipolar orthorhombic one. The polar phase can be recovered by annealing at $T>300\hspace{0.5em}{}^{°}$C. In accordance with neutron powder diffraction data, an inverse isothermal antipolar-polar transition takes place at $T>300$ ${}^{°}$C, where the polar phase becomes more stable. The antipolar phase is characterized by a weak ferromagnetic state, whereas the polar phase has been obtained in a mixed antiferromagnet–weak ferromagnet state. The relatively low external pressure induces polar-antipolar transition, but there is no evidence of electric-field-driven antipolar-polar transition. The observed large local piezoelectric response is associated with structural instability of the polar phase, whereas local multistate piezoelectric loops can be related to the domain wall pinning effect.

The structure and magnetic properties of the Ba-ordered state in solid solutions of manganites Ln0.70Ba0.30MnO3−δ (Ln = Pr, Nd) with a cation ratio Ln3+/Ba2+≫ 1 are studied experimentally. The...

The paper describes preparation features of functional composites based on ferrites, such as “Ba(Fe_1−xGa_x)₁₂O₁₉/epoxy,” and the results of studying their systems; namely, the correlation between structure, magnetic properties and electromagnetic absorption characteristics. We demonstrated the strong mutual influence of the chemical compositions of magnetic fillers (Ba(Fe_1−xGa_x)₁₂O₁₉ 0.01 < x < 0.1 solid solutions), and the main magnetic (coercivity, magnetization, anisotropy field and the first anisotropy constant) and microwave (resonant frequency and amplitude) characteristics of functional composites with 30 wt.% of hexaferrite. The paper presents a correlation between the chemical compositions of composites and amplitude–frequency characteristics. Increase of Ga-content from x = 0 to 0.1 in Ba(Fe_1−xGa_x)₁₂O₁₉/epoxy composites leads to increase of the resonant frequency from 51 to 54 GHz and absorption amplitude from −1.5 to −10.5 dB/mm. The ability to control the electromagnetic properties in these types of composites opens great prospects for their practical applications due to high absorption efficiency, and lower cost in comparison with pure ceramics oxides.