Activation volume and coercivity in aluminum-substituted Pb–M hexaferrites

• Published in: Journal of magnetism and magnetic materials 2000-12, Vol.222 (3), p.271-276
• Main Authors: Faloh Gandarilla, J.C, Dı́az-Castañón, S, Suárez Almodovar, N
• Format: Article
• Language: English
• Subjects: Activation volume; Aluminum substitution effects; Coercivity mechanisms; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Ferrimagnetics; Hexaferrites; Magnetic aftereffects; Magnetic properties and materials; Magnetic viscosity; Physics; Studies of specific magnetic materials
• ISSN: 0304-8853
• DOI: 10.1016/S0304-8853(00)00431-5

PbFe 12− x Al x O 19 samples were obtained by the chemical coprecipitation method with compositions x=0.0, 3.0, 4.0, 6.0. As was expected, significant differences in magnetization reversal mechanisms were found at room temperature in these specimens. A magnetic viscosity study was carried out in the temperature range of 75–300 K in order to obtain information related to the mechanism of magnetization behavior. A logarithmic time dependence of the magnetization was observed during a period of 20–1200 s. The magnetic viscosity S v and the activation volume V a increase as temperature is increased; the samples x=3.0 and 4.0 show the most rapid increase of the activation volume with temperature. Except for the samples x=3.0 and 4.0, the experimental temperature dependencies of the coercive field are in agreement with a model due to Givord and co-workers in which the magnetization reversal occurs in a volume equal to the activation volume.