Spin-Wave and Critical Neutron Scattering from Chromium

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Abstract
Chromium and its dilute alloys are unique examples of magnetism caused by itinerant electrons. The magnetic excitations have been studied by inelastic neutron scattering using a high‐resolution triple‐axis spectrometer. Spin‐wave peaks in q scans at constant energy transferℏω could, in general, not be clearly resolved at any temperature below TN but it is still possible to deduce the slope ω/q of the dispersion curve and also to estimate the spin‐wave lifetimes. The scattering displays a divergence as q→0, ω→0, T→TN characteristic of critical fluctuations. The critical scattering is confined to small values of q, but the ω range is very wide compared to critical scattering from systems with localized magnetic moments. The experimental results agree generally with the theoretical predictions of Liu [Phys. Rev. Lett. 23, 311 (1969); Phys. Rev. (to be published)].