Application of the Inverted-Neutron-Filter Technique to the Study of Inelastic Scattering by Paramagnetic Substances
Using the filter-cutoff method we have measured the quasielastic scattering of slow neutrons from several paramagnetic compounds. Our results for MnF2 at large scattering angles are in reasonable agreement with time-of-flight measurements by Cribier and Jacrot. For small scattering angles we have confirmed the Lorentz-like form of the energy distribution of scattered neutrons predicted by de Gennes. Similar measurements at large and small scattering angles on a partially inverted sample of MnAl2O4 did not exhibit the predicted angular dependence. This suggests that the assumption of A-A interactions only is inappropriate for this compound. From the temperature dependence of the intensity of the (200) magnetic reflection, a Néel temperature of 18°K was deduced for the MnAl2O4. Our results demonstrate that with an adequate flux of long-wavelength neutrons the inverted-filter technique can be employed successfully in studies of paramagnetic scattering.