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Hagi ware originally consists of a mixture of two raw materials: Daido clay and Mishima clay. During its firing process, we observed a change in the magnetic properties of the iron oxide, Fe2O3. The magnetic moment of the Daido clay (which only contains a small amount of the Fe2O3 γ-phase) attains a maximum at a firing temperature of approximately 600°C, where a minor amount of the poorly crystallized Fe2O3 temporarily changes to the ferromagnetic γ-phase. Furthermore, the magnetic moment of the Mishima clay (which contains a large amount of the Fe2O3 γ-phase) decreases as the firing temperature increases, whereas the coercive field rapidly increases at firing temperatures above 1000°C. The magnetization curve of the Mishima clay that was fired at temperatures above 1200°C is characteristic of a two-component system consisting of a minor γ-phase and a major α-phase. The above-mentioned phenomena were also confirmed by XRD analyses. A series of experiments indicated that the firing of Hagi ware can be characterized as a transformation from the γ-phase of Fe2O3 to the α-phase of Fe2O3. This transformation is considered to contribute to the change from soft magnetism to hard magnetism of Hagi ware.

SmCo 3 Cu 2 /α-Fe nanocomposites have been obtained by mechanical milling (MM) of a SmCo 3 Cu 2 +30 wt% α-Fe mixture and subsequent annealing. The progressive structural modifications were checked by X-ray diffraction (XRD). The width of the diffraction peaks of the hard magnetic phase was found to increase with milling time and the peaks almost disappeared after 9 h of milling. The characteristic diffractions peaks of the SmCo 5 -type phase could be restored by applying an appropriate heat treatment. The magnetic behavior of the SmCo 3 Cu 2 /α-Fe nanocomposite was studied versus milling and annealing conditions. A dramatic decrease in both the coercivity and the remanence was observed after milling. Considering the importance of the microstructure for the coercivity development in the SmCo 3 Cu 2 bulk alloys, the hard magnetic properties of the SmCo 3 Cu 2 /α-Fe nanocomposite are discussed in comparison with those characterizing bulk SmCo 3 Cu 2 .