ABSTRACT
In order to better present the spin glasses and establish their place in magnetic phenomenon, we should first consider how they evolved and where they belong with respect to other allied magnetic effects. Some perspective at this point is important and a number of cognate terms are in need of introduction. This chapter will briefly survey the related or surrounding phenomena from which the spin glasses developed. The main portion of Chapter 2 is devoted to the dilute magnetic alloys. Moment formation via the virtual-bound-state model and the Kondo effect along with the giant moments will be introduced. Afterwards we will discuss the various types of behaviour which appear in the different concentration regimes extending from very dilute to fairly concentrated. This is to show exactly where the spin glasses lie with respect to their disorder. Here a valuable new concept for us is percolation which distinguishes the spin glasses from the more-concentrated, long-range-ordered, random systems. Then we shall view the magnetic glasses, since amorphous magnetism is certainly a part of the spin-glass problem and many of these materials exhibit the novel ‘re-entry’ phenomenon. Finally, the notion of superparamagnetism is explored and its applicability to the spin glasses perused, and to conclude, the insulating and semiconducting systems will be mentioned and identified.
