CALCULATIONS OF (001)SURFACE SPIN-WAVES IN FRUSTRATED ANTIFERROMAGNETIC SYSTEMS WITH COMPETING EXCHANGE INTERACTIONS

Magnetic excitations on the (001) surface of simple cubic crystal have been studied in the case of semi-infinite Heisenberg frustrated antif erromanets, using the matching procedure methods. A detailed applicati on of the matching procedure is presented in order to calculate the su rface magnon. The magnon dispersion curve is calculated as a function of the frustration parameter J(AB)(1 nu)/J(AA(BB)(2 nu)), where J(AB)( 1 nu) and J(AA(BB)(2 nu)) represent the nearest and next nearest neigh bour exchange interactions, respectively. In this paper, we focus our attention on the values of J(AB)(1 nu)/J(2 nu)/(AA(BB)) > 4, a range f or which J(2 nu)/(AA(BB)) interactions are frustrated, while a magneti c phase transition is observed for J(1 nu)/((AB))/J(AA(BB)(2 nu) appro ximate to 4. When J1 nu/(AB)/J((AA(BB)(2 nu)) > 4, the behaviour of th e bulk magnon as well as acoustic and optical surface spin waves are v ery sensitive to the surface exchange and anisotropy. The evolution of acoustic and optical surface modes are interpreted by means of a frus tration parameter.