SPIN DYNAMICS IN THE QUANTUM ANTIFERROMAGNETIC CHAIN COMPOUND KCUF3

The magnetic excitations of a nearly ideal realization of a one-dimensional S = 1/2 Heisenberg antiferromagnet, KCuF3, have been studied by inelastic neutron scattering. The experiments were performed using the pulsed neutron source ISIS and show that the magnetic scattering occurs at energies well above the top of the linearized spin-wave band. This result shows that it is essential to take account of quantum effects in discussing the excitations. The results are in excellent accord with theoretical predictions for the dynamical correlation function.