Ferromagnetism microstructures

M. Fahnle and H. Kronmuller, "Micromagnetism and the Microstructure of Ferromagnetic Solids", Cambridge University Press, Cambridge 2003. 

So far, in this discussion, emphasis has been laid on the atomic interactions that lead to magnetic properties. Especially in ferromagnetic solids, the micro-stmcture of the solid is of importance and dominates applications. The microstructures found are the result of long-range interactions between the elementary magnets. For an isolated atom or ion with unpaired electron spins, no interaction occurs between the elementary magnets, and magnetic properties are reflected in a Curie law type of dependence. 

Pandey B, Ghosh S, Srivastava P, Kumar P, Kanjilal D, Influence of microstructure on room temperature ferromagnetism in Ni implanted nanodimensional ZnO films, J. Appl. Phys., 105,033909-5, 2009. 

In a solid state reaction at low temperatures a solid reactant may be entirely converted to a solid product that keeps the original structure of the reactant. In such a thermal process new nonequilibrium solids can be made that cannot form when the system would be close to equilibrium. The temperature cannot be too low so that the reaction remains possible (sufficient mobility), and it should not be so high as to prevent crystallization to equilibrium structures. This procedure is called chimie douce or soft chemistry. An example of chimie douce from industrial chemistry is the oxidation of magnetite (a mixed valence form of iron oxide, FCjOJ to the ferromagnetic y-Fe203 (maghemite) in a microstructure that renders it suitable for... 

Concept Check 20.6 It is possible, by various means (e.g., alteration of microstructure and impurity additions), to control the ease with which domain walls move as the magnetic field is changed for ferromagnetic and ferrimagnetic materials. Sketch a schematic B-versus-H hysteresis loop for a ferromagnetic material, and superimpose on this plot the loop alterations that would occur if domain boundary movement were hindered. 

---