Surface spin waves in superconducting and insulating ferromagnets

TL;DR

This paper investigates surface magnetization waves in superconducting and insulating ferromagnets, revealing differences in their spectra and robustness due to electromagnetic and plasmonic effects.

Contribution

It provides a comparative analysis of surface spin waves in superconducting versus insulating ferromagnets considering exchange, dipole, and retardation effects.

Findings

At large wave vectors, spectra are similar for both materials.

Superconductors have a finite gap separating surface waves from bulk modes.

Surface waves are more robust in superconductors at small wave vectors.

Abstract

Surface magnetization waves are studied on a semi-infinite magnetic medium in the perpendicular geometry. Both superconducting and insulating ferromagnets are considered. Exchange and dipole energies are taken into account, as well as retardation effects. At large wave vectors, the spectrum for a superconductor and insulator is the same, though for the former the branch is terminated much earlier than for the latter due to excitation of plasmons. At small wave vectors, the surface wave is more robust in the superconductor since it is separated from the bulk continuum by a finite gap.