Eddy current damping of a moving domain wall: beyond the quasistatic approximation

TL;DR

This paper investigates how eddy currents in conducting ferromagnets cause a retarding force on moving domain walls, revealing a history-dependent pressure that affects magnetic dynamics and noise measurements.

Contribution

It introduces a model accounting for history-dependent eddy current effects on domain wall motion, extending beyond the quasistatic approximation.

Findings

Eddy current pressure depends on the motion history, not just instantaneous velocity.

A negative effective mass describes the eddy current influence on the domain wall.

Sample geometry significantly affects the eddy current damping effect.

Abstract

In conducting ferromagnetic materials, a moving domain wall induces eddy currents in the sample which give rise to an effective retarding pressure on the domain wall. We show here that the pressure is not just proportional to the instantaneous velocity of the wall, as often assumed in domain wall models, but depends on the history of the motion. We calculate the retarding pressure by solving the Maxwell equations for the field generated by the eddy currents, and show how its effect can be accounted for by associating a negative effective mass to the magnetic wall. We analyze the dependence of this effect on the sample geometry and discuss the implications for Barkhausen noise measurements.