Spin-wave spectrum and inelastic neutron scattering by magnons inNd2CuO4

The spin-wave spectrum of the ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$ exchange-noncollinear four-sublattice antiferromagnet has been investigated theoretically. It is shown that there exists a quasi-two-dimensionality of the spin-wave spectrum when the wave vector is oriented along a certain direction. This quasi-two-dimensionality originates from a specific crystal and magnetic symmetry of ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$ and is in no way connected with the small values of some exchange parameters in comparison with others. Further, the inelastic neutron scattering by magnons in ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$ has been considered and the effects of the exchange enhancement of the scattering intensities for some particular Bragg peaks are analyzed.