Spin glasses have variously been described as apparently frozen but very slowly relaxing spin systems, and also as magnetic phases below a second order transition. The structural and dynamic properties of metallic spin glasses are surveyed with emphasis on neutron scattering and low field magnetic measurements. Spin glass regions in phases with magnetic long range order are included, and an attempt is made to assess spin glass theories with respect to the various transitions.

Magnetic order in metallic and nonmetallic binary alloys is discussed. A recent model, in which the breakdown of long-range magnetic order in metallic alloys is due to the cooperative change of the moment magnitude with concentration, is illustrated with. examples from nickel alloy systems. Percolation at the critical concentration for long-range order plays a part in these alloy systems, as it does for nonmetallic alloys and metallic alloys in which the magnetic moment magnitude is not so environment dependent. Discussion of the magnetic state in the non long-range ordered composition range leads to a description of spin glasses. The results of recent experiments on the low temperature configuration, the AC susceptibility near the freezing temperature, and the dynamics at all temperatures are presented with the implications for the nature of the spin glass transition.