ABSTRACT
While it is not the purpose of this chapter to consider all 500-plus materials, nevertheless, we wish to list the most important spin-glass categories and to distinguish their class according to the strength of the magnetic interactions which are present. Remember the conduction-electronmediated RKKY interaction of the transition-metal impurities have the strongest coupling. Oppositely, superparamagnets (rock magnets or Co0 particles) have little or no coupling and are, therefore, not spin glasses.
