On the microstructure and magnetization process of γ-Fe2O3

Experimental evidence is reported for γ-Fe2O3single particles being made up of several microcrystals chained together and their boundaries being sources of demagnetizing fields. This leads to a very defined picture of the magnetization reversal in partially alligned γ-Fe2O3particles: rotation is incoherent but the magnetization vectors are scattered in such a way that Hcivs. angle Ψ (between the orientation direction and the applied field) does not follow the known magnetization reversal modes. The importance of the reduction temperature in the process: α-FeOOHunderrightarrow{red.}Fe3O4underrightarrow{ox.}γ-Fe2O3becomes extremely important if considered as the parameter which rules the pore closure within the particles, i.e. the size and number of microcrystals chained in a single particle.