Spin-Wave and Critical Neutron Scattering from Chromium

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)].