Paramagnetic scattering from metallic Ni

We have succeeded in establishing a reliable scattering function $S(Q,\omega )$ for paramagnetic nickel in the range up to $\Delta E=50\mathrm{}$ meV, $q=0.4\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$, and $T=1.24\mathrm{}{T}_C$. These studies were performed mainly with unpolarized neutrons, but the polarization analysis was also utilized to completely separate the magnetic cross section. We show that the main part of the magnetic scattering has the form of a broad Lorentzian centered at zero energy transfer. In constant-$Q$ scans, no intensity enhancement was observed at the expected persistent spin-wave position reported by Lynn and Mook. Although constant-$E$ scans show well-defined peaks in agreement with the results of Lynn and Mook, these scans do not signify the existence of persistent spin waves above $T_C$. The magnetic intensities have been put on an absolute scale by comparing with known phonon and magnon cross sections. In this way, we have derived the paramagnetic response $M^2\mathrm{}\left(Q\right)\mathrm{}$ which is Lorentzian in $\overrightarrow{\mathrm{q}} (=\overrightarrow{\mathrm{Q}}-\overrightarrow{\tau })$ with correlation lengths that, unexpectedly, correspond to extrapolated values found in the critical region.