Magnetic excitations in antiferromagnetic Mn1-cZncF2at large Zn concentrations

Neutron inelastic scattering techniques have been used to study Zn-substituted MnF 2 crystals with average Zn concentrations c=0.22+or-0.02 and 0.7+or-0.1. For c=0.22 the results gave scattered distributions whose peaks were at frequencies less than those of the excitations of pure MnF 2 and whose width was considerably larger than the experimental resolution. The other specimen had a concentration gradient such that one end of the crystal ordered magnetically at 4.2K whereas the other end did not. There were no significant differences between the scattering from the different ends, and it consisted of an overdamped distribution the width of which decreased as the wavevector of the excitation decreased.