Influence of charge disproportionation on microwave characteristics of Zn–Nd substituted Sr-hexaferrites

• Published in: Journal of materials science. Materials in electronics Vol. 30; no. 7; pp. 6776 - 6785
• Main Authors: Almessiere, M. A., Genc, F., Sozeri, H., Baykal, A., Trukhanov, S. V., Trukhanov, A. V.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.04.2019; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Crystal structure; Disproportionation; Electrodynamics; Ferric ions; Ferromagnetic resonance; Ferromagnetism; Magnetic permeability; Materials Science; Optical and Electronic Materials; Oxidation; Permeability; Permittivity; Rangefinding; Sol-gel processes; Substitutes; Valence
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-019-00989-8

Sr(Zn,Nd) x Fe 12−x O 19 (0.0 ≤ x ≤ 1.0) nanohexaferrites (NHFs) were obtained using citrate sol–gel approach. XRD and FE-SEM analysis were performed to confirm the formation of Sr M-type hexaferrite. Main electrodynamics characteristics (frequency dependences of real and imaginary parts of the permittivity and permeability) were measured in the range 5–18 GHz (region of the natural ferromagnetic resonance). Permittivity and permeability data correlates well. All samples were characterized by peak on the frequency dependences due to electrical and magnetic losses respectively. However, for compounds with x = 0.1 and 0.9 we observed second peak (at 14–15 GHz). This was explained by double oxidation state for iron ions (Fe 3+ /Fe 4+ ). Presence of the Fe 4+ ions was due to heterovalent Zn 2+ substitution. Absence of the second peak for compounds x = 0.3; 0.5 and 0.7 was explained by charge disproportionation (according to the following scheme: 2Fe 4+  = Fe 3+  + Fe 5+ ) under the influence of the crystal field energy. It was demonstrated that modification of crystal and magnetic structures by heterovalent substitution leads to transformation the microwave characteristics (reflection losses).