Domain-Wall Waves (2D Magnons) in Superconducting Ferromagnets

TL;DR

This paper theoretically investigates how superconductivity influences the propagation of domain-wall magnetization waves in ferromagnets, highlighting the effects of Meissner currents on the magnon spectrum and proposing impedance measurements for experimental probing.

Contribution

It introduces a theoretical model showing how superconducting currents modify 2D magnon spectra and suggests a new experimental approach to study superconductivity-ferromagnetism coexistence.

Findings

Superconducting Meissner currents screen magnetostatic fields.

Long-wavelength spectrum shifts from square-root to linear due to superconductivity.

Surface impedance measurements can probe domain wall waves.

Abstract

Propagation of the magnetization waves along domain walls (2D magnons) in a superconducting ferromagnet has been studied theoretically. The magnetostatic fields (long-range dipole-dipole interaction) have a crucial effect on the spectrum of 2D magnons. But this effect is essentially affected by the superconducting Meissner currents, which screen the magnetostatic fields and modify the long-wavelength spectrum from square-root to linear. The excitation of the domain wall waves by an electromagnetic wave incident on a superconducting-ferromagnet sample has been considered. This suggests using measurements of the surface impedance for studying the domain wall waves, and eventually for effective probing of superconductivity-ferromagnetism coexistence.