NEUTRON STUDY OF FRACTON EXCITATIONS IN PERCOLATING ANTIFERROMAGNETS

We report the results of an inelastic neutron scattering experiment on nearly percolating Heisenberg antiferromagnets (RbMncMg1-cF3), in whi ch the Mn concentrations (c = 0.31, 0.34 and 0.39) are very close to t he percolation threshold (c(p) = 0.312). A broad-peak superimposed on Ising-cluster excitations was observed throughout the Brillouin zone. The intensity of a broad peak increased on approaching the percolation threshold. The origin of this broad peak is attributed to the excitat ion of fractons in a percolating network. (C) 1998 Elsevier Science B. V. All rights reserved.