Cómo mejorar las propiedades magnéticas de las hexaferritas

BERCOFF, P.G; C. HERME; JACOBO S.E.

Tucumán

Congreso; Sólidos; 2011

Ever since their discovery by Philips between 1952 and 1956, M-type ferrites have increasingly become of great interest for applications such as permanent magnets, plastoferrites, injection moulded pieces, microwave devices and magnetic recording media. It has been reported by different authors that the saturation magnetization as well as the magnetocrystalline anisotropy constant of M-type ferrite fine particles increase by the substitution of rare earths. However, the solubility of rare earth ions in Sr-hexaferrites is very low and their addition leads to the formation of secondary phases, which must be avoided in order to obtain permanent magnets with optimal properties. As hematite and different iron compounds appear to be the main secondary phases when rare-earth ion substitution increases, we proposed different formulations with iron deficiency. In this seminar we will explore the results obtained on the structure and magnetic properties of non-stoichiometric Nd-Co doped strontium hexaferrite samples prepared by the self-combustion method. We will see that the samples with lower iron content show the highest saturation magnetization and/or coercivity, indicating that the best results for applications of this ferrite will be obtained with an iron deficiency in the stoichiometric formulation. Nd substitution enhances the ferrite anisotropy and coercivity with respect to the unsubstituted sample.