Dynamics of a spiral magnetic structure in an external magnetic field

Static and dynamic properties of a magnet with an easy-plane anisotropy with a spiral magnetic structure placed in an external magnetic field have been analyzed. The energy spectrum and the amplitudes of linear spin excitations have been calculated for this structure. Their field dependences have been analyzed in detail. Tensors of the local and integral dynamic magnetic susceptibilities have been derived. The spin-wave contributions to the temperature-field dependence of the magnetization have been calculated. The possibility of applying the results obtained to the study of NMR in magnets with a spiral magnetic structure is discussed.