NONLINEAR EXCITATIONS IN THE FCC ANTIFERROMAGNET CEAS

Employing the Dyson-Maleev transformation, the coherent state ansatz and the time-dependent variational principle, we obtain two partial differential equations of motion from the Hamiltonian in the fee antiferromagnet CeAs. By using the multiple scalar method and long-wavelength approximation, we reduce these equations to an envelope function equation, and we force this function to satisfy the nonlinear Schrodinger equation. The single and two soliton bound state solutions are obtained by using the inverse scattering transformation. For the single and two soliton bound state, the spatial configurations of the spin are given. These results show that the nonlinear magnon localization and the two magnon bound state are possible in this system. The possibility of observing a gap soliton is also discussed.