Influence of the charge ordering and quantum effects in heterovalent substituted hexaferrites on their microwave characteristics

Abstract M-type hexagonal ferrites with heterovalent substitutions (Nd 3+- Zn 2+ and Ti 4+ ) were synthesized. X-Ray diffraction (XRD) powder patterns of Sr(Nd,Zn) x Fe 12-x O 19 and BaFe 12-x Ti x O 19 (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 Fe 12-x O 19 (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 Fe 12-x O 19 and BaFe 12-x Ti x O 19 (0.1 ≤ x ≤ 1.0) samples was discussed in terms of the modalities of charge ordering in heterovalent substituted M-type hexaferrites.