Magnetic-field-sensing mechanism based on dual-vortex motion and magnetic noise

Abstract

In this study, we report two novel field sensing mechanisms using elliptical permalloy single layer. Using micromagnetic modeling, dual-vortex structure is observed and stabilized in elliptical permalloy single layer by applying hard bias field (along the y-axis) and vertical axis field (perpendicular to plane). During the increasing or decreasing of the hard bias field within certain range, the dual vortices would move away from or approach to each other at a constant velocity, leading to a positive correlation between the hard bias field and the vortex gap. By exploring the magnetic noise properties of the elliptical permalloy single layer under various vortex gap, the vortex gap is found to be positively correlated with both the FMR (Ferromagnetic Resonance) peak positions and the integrated thermally excited mag-noise. Therefore, the combination of the dual-vortex motion and the magnetic noise properties make it possible to measure external field (along hard bias direction) through measuring the FMR peak positions or integrated thermally mag-noise. This FMR-peak-based field sensing mechanism and integrated-noise-based field sensing introduce a simple field sensor structure with expected highest sensitivity to 1.1%/Oe and field detectable range over 1000 Oe, which is promising for potential sensor applications.