Spin dynamics in the two-dimensional antiferromagnetLa2CuO4

The magnetic dynamics of ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$ have been studied by means of inelastic neutron scattering in the energy range 0≤ħω≤140 meV. Experiments were carried out using a wide range of incident neutron energies so as to optimize the experimental resolution in each energy range studied. For energy transfers, ħω≥10 meV, and temperatures T in the range 5≤T≤320 K, we find that conventional spin-wave theory gives a good description of the magnetic dynamics. We obtain a low-temperature spin-wave velocity ħc=850±30 meV Å. For low energies, ħω≤10 meV, and temperatures corresponding to the paramagnetic phase, our data indicate a response function consisting of overdamped spin waves and a quasielastic peak.