The Magnetization Process In Monoclinic Pyrrhotite (Fe7S8) Particles Containing Few Domains
Year: 1991
Type: article
Abstract: Monoclinic pyrrhotite was prepared by the silica tube technique. All characteristic properties (X-ray, magnetic) point to the successful synthesis of Fe7S8. The material was separated into seven size fractions in the particle size range 1–30 µm, in which the particles are believed to contain only few domains. the magnetization process was studied at room temperature. the characteristics of the finest fraction (<0.8 µm) are consistent with coherent rotations of monodomain moments and a triaxial symmetry of anisotropy within the basal plane. The in-plane anisotropy constant is about 3 × 103 Jm-3. In the sized fractions (1–30 µm) the variation of ratio of isothermal remanence to saturation magnetization (Mrs/Ms) can be fitted by models of increasing complexity based on the statistically expected number of domains in particles of a particular size. the data can also be fitted by (Mrs/Ms) = 0.52 exp(-0.047L1/2) where L is the mean particle size in µm. The form of this expression is suggestive of the relevance of Poisson statistics to the magnetization process, but the numerical parameter within the exponential is physically implausible. Unlike titanomagnetite (Fe2.4 Ti0.6O4) particles of the same size range, the variation of coercive force (Hc) cannot be modelled on the basis of independent surface and volume pinning of domain walls. There is evidence for only one wall pinning mechanism in the 1–30 µm range in Fe7S8. A pleasing fit to the data is obtained by Hcr, = 75.5 exp(-0.025L1/2)kA m-1. A similar dependence is found for Hcr, the coercive force of isothermal remanence. The susceptibility in the 1–30 µm range appears to be essentially the ‘intrinsic’ susceptibility and, if so, again provides evidence for only one wall pinning mechanism.
Authors: A. Menyeh, W. O'reilly
Institution: Newcastle University
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2079856415