Field theory of linear spin waves in finite textured ferromagnets
Phys. Rev. B 113, 104437 – Published 19 March, 2026
DOI: https://doi.org/10.1103/qyr8-9817
Abstract
In the context of an ever-expanding experimental and theoretical interest in the magnetization dynamics of mesoscopic magnetic structures, both in the classical and quantum regimes, we formulate a low-energy field theory for the linear spin waves in finite and textured ferromagnets and we perform its constrained canonical quantization. The introduction of a manifestly gauge invariant Lagrangian enables a straightforward application of the Noether's theorem. Taking advantage of this in the context of a broad class of axisymmetric ferromagnets of special conceptual and experimental relevance, a general expression of the conserved and quantized spin-wave total angular momentum is rigorously derived, while separate conservation and quantization of its orbital and spin components are established for a more restricted class of uniaxial exchange ferromagnets. Further particularizing this general framework to the case of axially saturated magnetic thin disks, we develop a semianalytic theory of the low-frequency part of the exchange-dipole azimuthal spin-wave spectrum, providing a powerful theoretical platform for the analysis and interpretation of magnetic resonance experiments on magnetic microdots as further demonstrated in a joint paper [Phys. Rev. B 113, L100410 (2026)].
