On the velocity of sound in an itinerant-electron antiferromagnet

The longitudinal sound velocity in an itinerant-electron antiferromagnet is studied, using a jellium model for the ions and a two-sub-band model for the itinerant electrons with an energy gap caused by the antiferromagnetic spin ordering. It is shown that the longitudinal sound velocity decreases with decreasing temperature, due to the electron-photon interaction. The exchange interaction between itinerant electrons is seen to play a particularly important role in the phonon softening phenomena for such a system; and although the model is a great simplification of reality it gives reason to believe that the observed elastic anomalies in the face-centred-cubic 3d transition metal alloys are directly related to their tendency towards antiferromagnetism.