Bulk and surface spin waves of the superantiferromagnetic ground-state Heisenberg system

Abstract

A formalism for calculating the bulk and surface spin waves in the ground-state frustrated superantiferromagnetic Heisenberg system is presented. The magnetic structure consists of semi-infinite ferromagnetic chains which are antiferromagnetically coupled. The surface spin-wave theory introducing the matching method is used to calculate the energy of the surface magnon. The magnon dispersion curve is calculated as a function of the frustration parameter and the bulk - surface exchange ratio . The behaviour of the bulk magnon as well as the acoustic and optical surface modes which are found to be very sensitive to the surface exchange and anisotropy are interpreted by means of a ratio. The results show that a high instability of bulk and surface spin precession occurs for , and disappears for . The latter value corresponds to an antiferromagnetic arrangement of the ground state.