Vortex Viscosity in Magnetic Superconductors Due to Radiation of Spin Waves

TL;DR

This paper investigates how vortices in magnetic superconductors emit spin waves, leading to additional magnetic viscosity that affects vortex dynamics and results in observable anomalies in current-voltage behavior.

Contribution

It introduces the concept of vortex-induced spin wave radiation as a source of magnetic viscosity, highlighting its threshold behavior and impact on superconductor dissipation.

Findings

Vortex motion can radiate spin waves, increasing magnetic viscosity.

A threshold current exists for spin wave radiation, similar to Cherenkov radiation.

Radiation causes anomalies in current-voltage characteristics and reduces dissipation.

Abstract

In type-II superconductors that contain a lattice of magnetic moments, vortices polarize the magnetic system inducing additional contributions to the vortex mass, vortex viscosity, and vortex-vortex interaction. Extra magnetic viscosity is caused by radiation of spin waves by a moving vortex. Like in the case of Cherenkov radiation, this effect has a characteristic threshold behavior and the resulting vortex viscosity may be comparable to the well-known Bardeen-Stephen contribution. The threshold behavior leads to an anomaly in the current-voltage characteristics, and a drop in dissipation for a current interval that is determined by the magnetic excitation spectrum.