Abstract
M-type hexagonal ferrites with heterovalent substitutions (Nd3+-Zn2+ and Ti4+) were synthesized. X-Ray diffraction (XRD) powder patterns of Sr(Nd, Zn)(x)Fe12-xO19 and BaFe12-xTixO19 (0.1 <= x <= 1.0) confirmed the single phase constitution of all investigated samples. High frequency magnetic (permeability), electrical (permittivity), and resonant properties were analyzed. Unexpected behavior in the permittivity and permeability as a function of frequency was observed. Appearance of two peaks for samples with x = 0.1 and 0.9 indicated mixed oxidation state for the Fe ions. Behavior for Sr(Nd, Zn)(x)Fe12-xO19 (0.3 <= x <= 0.7) confirms the occurrence of the anomalous quantum effect, namely charge disproportionation. The permeability behavior of Ti-substituted samples with a double Fe oxidation state was theoretically discussed in terms of spin states crossover. The behavior of reflection losses for Sr(Nd, Zn)(x)Fe12-xO19 and BaFe12-xTixO19 (0.1 <= x <= 1.0) samples was discussed in terms of the modalities of charge ordering in heterovalent substituted M-type hexaferrites. (c) 2019 Elsevier B.V. All rights reserved.