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Present paper reports about the strong correlation of the heat treatment conditions (annealing), crystal structure parameters, microstructure and magnetic properties evolution in nanosized BaFe 12 O 19 M-type hexaferrites or BaM nanohexaferrites. Samples of the BaM nanohexaferrites were obtained using sol-gel method with further annealing in the range 600–1100 °C. All investigated samples were single phase and described by the P 6 3 / mmc space group. Unusual and non-linear behavior of the lattice parameters with annealing temperature increasing from 600 to 1100 °C was explained by the competition of the increase in the average crystallite size (decrease in the surface tension effect) and increase in the level of their chemical homogeneity (anionic stoichiometry). Increase of the heat treatment temperature leads to increase of the microstructure parameters (average crystal size and specific surface area) and non-linear changes in magnetic properties. Correlation of the annealing temperature and magnetic properties was discussed in terms of the structural features. • BaM nanohexaferrites were synthesized using sol-gel method with further annealing. • Strong correlation between average crystal size and annealing temperature was established. • Non-linear behavior of the structure and magnetic properties after annealing was observed. • All changes in BaM were discussed in terms of the morphology evolution. [ABSTRACT FROM AUTHOR]

As produced glass-coated ferromagnetic microwires typically have an amorphous state and demonstrate ultra-soft magnetic properties. For many applications, microwires with strong hard magnetic properties are of interest. A giant increase in coercivity has been recently reported for microwires subjected to directed crystallization. This paper confirms the coercivity increase up to 42 kA/m for wires of composition Fe 4.3 Co 67.7 Si 11 B 14 Cr 3 after magnetic-field assistant directed crystallization. To understand the effect of the directional crystallization on wire magnetic properties and to develop the reliable annealing technology the structural and mechanical transformation occurring during various stages of the annealing processes were investigated. [ABSTRACT FROM AUTHOR]

M-type BaFe 11.9 Al 0.1 O 19 hexaferrite was successfully synthesized by solid state reactions. Precision investigations of crystal and magnetic structures of BaFe 11.9 Al 0.1 O 19 powder by neutron diffraction in the temperature range 4.2–730 K have been performed. Magnetic and electrical properties investigations were carried out in the wide temperature range. Neutron powder diffraction data were successfully refined in approximation for both space groups (SG): centrosymmetric #194 (standard non-polar phase) and non-centrosymmetric #186 (polar phase). It has been shown that at low temperatures (below room temperature) better fitting results (value χ 2 ) were for the polar phase (SG: #186) or for the two phases coexistence (SG: #186 and SG: #194). At high temperatures (400–730 K) better fitting results were for SG: #194. It was established coexistence of the dual ferroic properties (specific magnetization and spontaneous polarization) at room temperature. Strong correlation between magnetic and electrical subsystems was demonstrated (magnetoelectrical effect). Temperature dependences of the spontaneous polarization, specific magnetization and magnetoelectrical effect were investigated. [ABSTRACT FROM AUTHOR]

• In-substituted SrM hexaferrites were synthesized using solid state reactions. • Coexistence of the electrical and magnetic ordering at room temperature was observed. • Formation of the bevelled magnetic structure was no detected. • The reason of the ferroelectricity was discussed in the frame of P 6 3 mc space group. The local crystal/magnetic structures of the SrFe 12−x In x O 19 solid solutions (x = 0.1; 0.3; 0.6 and 1.2) were investigated using neutron powder diffraction. The measurements of the electric polarization for all investigated samples were carried out as a function of the external electric field. The presence of the ferroelectric and ferromagnetic ordering (dual ferroic ordering) in the SrFe 12−x In x O 19 hexaferrites at 300 K was found. This appearance contradicts to the conventional opinion describing their crystal structure (centrosymmetric space group P 6 3 /mmc (No. 194)). The reason for the existence of a spontaneous polarization (nonzero dipole moment) in the SrFe 12−x In x O 19 hexaferrites continues controversial. The crystal structure of the hexaferrites was considered both the centrosymmetric P 6 3 /mmc and non-centrosymmetric P 6 3 mc space groups. This fact made it possible to find a connection between the emerging dipole moment and not equal distortions of the neighbor oxygen polyhedral. The nature description of the nonzero dipole moment formation in a quasi-centrosymmetrical system of the In-substituted SrFe 12−x In x O 19 hexaferrites was presented based on the neutron diffraction data. [ABSTRACT FROM AUTHOR]