High-frequency magnetic susceptibility of an antiferromagnet with magnetic anisotropy of the easy-plane type

On the basis of the representation of spin operators in terms of boson operators introduced by V. G. Baryakhtar and D. A. Yablonsky the hamiltonian of magnon-magnon interactions of an easy-plane antiferromagnet is studied. It is shown that the amplitudes of the processes including the Goldstone magnons satisfy the Adler principle. Tensor of high-frequency magnetic susceptibility is calculated.