Polarized-beam study of the paramagnetic scattering from bcc iron

摘要: Reliable magnetic scattering cross sections are obtained for bcc Fe at $T=1.02{T}_{c}$ and $1.06{T}_{c}$ using polarized neutrons polarization analysis. The constant-$q$ measurements cover a $q$ range of 0.1-0.6 ${\mathrm{\AA{}}}^{\ensuremath{-}1}$ with an energy extending up to 50 meV. These scans consist broad distributions centered zero no peaks observed finite-energy transfers, in contrast the results reported by Lynn. A simple paramagnetic function $S(q,\ensuremath{\omega})\ensuremath{\propto}[\frac{1}{({\ensuremath{\kappa}}_{1}^{2}+{q}^{2})}][\frac{\ensuremath{\Gamma}}{({\ensuremath{\Gamma}}^{2}+{\ensuremath{\omega}}^{2})}]$ is shown describe iron quantitatively, absolute units, specified above. constant-energy simply slices thus should not be interpreted as spin-wave peaks. We conclude that ($q$,$\ensuremath{\omega}$) region covered our beam studies, neither propagating spin waves nor giant short-range order exist above ${T}_{c}$.