Spatial mapping of magnetization fluctuations via time-lapse Kerr microscopy

TL;DR

This paper introduces a high-resolution Kerr microscopy technique combined with time-lapse analysis to spatially map magnetization fluctuations in ferromagnetic films, revealing localized noise hotspots and enabling detailed study of magnetic noise processes.

Contribution

The study presents a novel method for spatially and temporally resolving magnetization fluctuations in magnetic materials using Kerr microscopy and time-lapse analysis.

Findings

Identification of spatially localized noise hotspots within magnetic domains

Noise hotspot density remains consistent across different low magnetic fields

Technique enables detailed spatially resolved analysis of magnetic noise processes

Abstract

Combining wide-field magneto-optical Kerr microscopy with a time-lapse analysis scheme allows investigating magnetization fluctuations with high spatial as well as temporal resolution. We here use this technique to study magnetization fluctuations in a thin ferromagnetic film prepared into a quasi-equilibrium magnetic state via a dedicated field sweep protocol. Our experiments reveal spatially localized noise hotspots distributed across the sample surface within the magnetic domains in the quasi-equilibrium state. The spatial density of the noise hot spots is very similar at different low magnetic field strengths, as expected from the fluctuation-dissipation theorem. The measurement scheme thus opens the way for the spatially resolved investigation of quasi-equilibrium noise processes in magnetic materials.