DISPERSION OF SPIN-WAVES IN THE S = 1/2 SQUARE HEISENBERG-ANTIFERROMAGNET CU(DCO2)2.4D2O

We present inelastic neutron scattering measurements of the dispersion of magnetic excitations within and between the magnetic layers of the insulating S=1/2 square Heisenberg antiferromagnet copper (II) formate tetradeuterate (Cu(DCO2)2·4D2O). At the antiferromagnetic zone centre is an excitation at (0.60±0.05) meV which does not appear to disperse along c*. Dispersion is seen along b*. The dispersion curve was fitted to a spin-wave expression and yielded values for the intraplane exchange of (9.3±0.1) meV. © 1992