DIFFUSE-MAGNETIC-SCATTERING CALCULATIONS FOR FRUSTRATED ANTIFERROMAGNETS

A method based on the Gaussian approximation is presented for calculating the magnetic neutron scattering from short-range-ordered magnetic systems. Scattering profiles are calculated for three highly frustrated systems: the rhombohedral-, kagome-, and pyrochlore-lattice antiferromagnets. The results are compared with those obtained from conventional Monte Carlo techniques and with recent experimental results for FeF3 and Tb2Mo2O7. For the rhombohedral lattice, the calculations predict two-dimensional peaks even in the presence of strong interplanar interactions and provide an explanation for the lack of observed wide-angle magnetic neutron scattering in LiNiO2. Scattering consistent with short-range order is predicted for the pyrochlore- and kagome-lattice antiferromagnets down to very low temperatures. The Monte Carlo method is most successful for treating truly short-range-ordered systems and low-dimensional systems. The Gaussian approximation method gave similar results for these systems and was also found to be useful for three-dimensional systems with quasi-low-dimensional order where the Monte Carlo method was impractical.