Dipole-exchange spin waves in rectangular antiferromagnetic nanowires

Abstract

A microscopic theory is developed for the dipole-exchange spin waves in long antiferromagnetic nanowires, either singly or in a rectangular array of size M×N, where M and N are arbitrary integers (typically chosen to be less than about 20). The model includes exchange interactions (both intrawire and interwire), the long-range dipole–dipole interactions, single-ion anisotropy (which stabilizes the antiferromagnetic ordering) and a longitudinal applied magnetic field. The spectrum of discrete coupled spin waves is calculated using a method similar to that employed recently to find the dipole-exchange spin waves in ultrathin antiferromagnetic films, and the spin-flop phase transition in some of these cases is also studied. It is found that the spin-wave frequencies are shifted as a result of the dipolar terms and that the transition field to the spin-flop phase is typically reduced in magnitude compared to its value in the exchange limit. The results are illustrated with numerical examples.