Moessbauer investigations of γ-Fe2O3 particles

Microcrystals of γ-Fe2O3 powder in the size range of single domain particles showing broadened six-line patterns at room temperature in zero applied field were found to behave purely superferromagnetic without any superparamagnetic portion. The broadened patterns have been interpreted on the basis of independent-uniaxial particles with unequal magnetization direction probability which undergo relaxation. Addition of alkaline, dotation with Zn2+ ions and coating by SiO2 cause further line broadening due to relaxation phenomena. The application of a magnetic field did not narrow the line width. This is taken as evidence for incomplete orientation of the magnetization vectors along the direction of the magnetic field. The microcrystals are assumed to subdivide in subdomains which probably possess a size distribution. (orig.)