Spin wave analysis of Heisenberg magnets in restricted geometries

Abstract

In the last decade it has been proven that the standard spin wave theory was able to provide accurate zero-temperature results for a number of low-dimensional Heisenberg spin systems. In this chapter we introduce the main ingredients of the spin-wave technique using as a working model the two-leg mixed-spin ferrimagnetic ladder and the Dyson--Maleev boson formalism up to second order in the spin-wave interaction. In the remainder, we survey typical applications in low-space dimensionality as well as some recent modifications of the theory admitting a quantitative analysis in magnetically disordered phases. The presented spin-wave results are compared with available numerical estimates.