Antiferromagnetism in Chromium and its Alloys

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Abstract
Recent experimental and theoretical work on itinerant antiferromagnetism in Cr and its alloys is reviewed with particular emphasis on optical and pressure effects. At low temperatures, a peak appears in the infrared conductivity of Cr which is attributed to excitation of electrons across the antiferromagnetic energy gap. The maximum in absorption occurs at photon energy 5.1kTN, at low temperatures, which is substantially higher than the value 3.5kTN predicted by the simplest models. Both the position and shape of the absorption can be explained if the effects of electron-phonon scattering are incorporated in the model. The pressure dependence of the Néel temperature of Cr and alloys with Mo and V is described. The role of band structure is discussed, particularly its effect on the vanishing of antiferromagnetism under pressure.