Spin-density wave in spin glasses (C uMn) and other dilute alloys (YGd)

Abstract

Spin glasses have been of particular interest in magnetism for the past 15 years. Their present theoretical description, based upon a simple physical model, requires a fundamentally new type of statistical mechanics for its solution. Most experimental interpretations have attempted to follow this approach, although its physical meaning and direct comparison are partially obscured and somewhat strained. Almost 30 years ago Overhauser proposed a spin-density-wave (SDW) model which endeavored to explain the ‘‘antiferromagnetic’’ behavior in dilute alloys such as CuMn. In the intervening period the spin-glass phenomenon has mainly evolved unconnected with the SDW approach. However, in recent times a series of neutron-scattering experiments has renewed the connection and introduced the distinction between a ‘‘long-range’’ SDW as found in YGd and the ‘‘short-range’’ SDW of the spin glasses, e.g., CuMn. It is the purpose of this paper to review the available evidence for a SDW mechanism in these dilute alloys relying not only on neutron-scattering data, but also on macroscopic measurements such as specific heat, magnetization, and susceptibility. Here clear-cut differences arise between the long-range and short-range SDWs which are related to the glassy dynamics of the latter systems.