Inference of domain structure at elevated temperature in fine particles of monoclinic pyrrhotite (Fe7S8).

Abstract

The thermal variation of the number of domains (nd) for Fe7S8 particles (within the size range 1-30 mm and between 20 and 300°C), has been inferred from the room temperature analytic expression between nd and particle size (L), the temperature dependences of the anisotropy energy constant (K) and the spontaneous magnetization (Ms) and, an assumed expression for the domain wall energy (Ew). It is found that nd increases or decreases with temperature rise depending on whether the inferred K(T) dependence is based on many defects in a domain wall, controlled by the volume reduction effect or the magnetostatic effect respectively. In either case however, nd is very weakly dependent on T which therefore points to a fixed domain multiplicity in the Fe7S8 particles within the temperature range specified. Based on this conclusion, it is suggested that the nucleation or denucleation of domain walls may be difficult processes in the acquisition of thermoremanent magnetization (TRM) in Fe7S8 particles.

JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 1, July (1998) pp. 118-125