Neutron Scattering by Coupled Paramagnetic Ions

Abstract

The paramagnetic scattering of very low energy neutrons by Mn${\mathrm{F}}_2$ and MnO was studied at various sample temperatures. The assumption of Van Vleck that a Gaussian distribution can be used to represent the frequency of inelastic scattering events versus energy transfer with the spin lattice is used, and the root mean square half-width of the distribution of energy transfer for Mn${\mathrm{F}}_2$ is found to be 0.0020, 0.0026, and 0.0034 ev at 610°, 300°, and 126°K, respectively. Short-range order scattering modifies the scattering cross section for Mn${\mathrm{F}}_2$ to the extent of $\frac{1.5}{4\pi }$ barns/steradian at 126°K, but is not observed at higher temperatures.