SPIN-WAVE EXCITATIONS IN FRUSTRATED ONE-DIMENSIONAL ANTIFERROMAGNETS KCU1-CMNCF3

The spin dynamics in the frustrated nearly one-dimensional antiferroma gnets KCu1-cMncF3 have been investigated by time-of-flight inelastic n eutron scattering. Although the sample with a small Mn concentration s hows antiferromagnetic ordering, well-defined collective excitations s uch as quantum spin excitations seen in pure KCuF3 can hardly be found in the mixed systems (c = 0.015 and 0.055).