Synthesis and Characterization of Ni-Ti Partially Substituted Hexaferrites for High-Density Magnetic Recording Applications

Abstract

Executive AbstractM-type hexaferrite (AFe₁₂O₁₉; A = Ba²⁺, Sr²⁺, Pb²⁺) is an important magnetic oxide exhibitingmagnetic properties suitable for a wide range of technological and industrial applications. The magnetic properties of M-type hexaferrite can be tuned for a specific application by adopting suitable synthesis routes and/or using special cationic substitutions for either Fe³⁺or A²⁺cations. In particular,coercive fields in the range of ~ 1 – 3 kOe and remnant magnetization > 20 emu/g are required for data storage media in high-density magnetic recording applications. Partial substitution of Fe³⁺ions by Co²⁺-Ti⁴⁺ ions in BaM (BaFe₁₂O₁₉) or SrM (SrFe₁₂O₁₉) hexaferrite was long recognized as an effective procedure for reducing the coercivity to values appropriate for high- density magnetic recording, without decreasing the remnant magnetization appreciably. Also, the effects of other substitutions were extensively investigated. However, the M-type hexaferrite with Ni²⁺-Ti⁴⁺ substitution was generally ignored, especially when compared with the extensively investigated Co2+-Ti4+ substituted system. This work was motivated by the potential of Ni-Ti substitution to reduce the coercivity of SrM hexaferrite to appropriate levels and maintain the remnant magnetization high enough for high-density magnetic recording applications. 

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Keywords: Hexaferrites, Partial substitution, Nickel, Titanium, High-density magnetic recording.