A Magnetoelastic Twist on Magnetic Noise: The Connection with Intrinsic Nonlinearities

Abstract

Intrinsic magnetic noise limits the functionality of all magnetic field sensors and related devices using magnetic films as sensing elements. A novel origin of magnetic noise due to ferromagnetic material's magnetostriction is revealed by implementing a comprehensive multi‐level signal‐noise model and thoroughly validating it experimentally on magnetoelectric composite ΔE‐effect sensors. From electrical measurements and operando magnetic domain visualization, magnetic contributions are shown to dominate the noise floor and limit the overall performance of multi‐domain magnetoelastic sensors. The newly introduced noise contribution is correlated with the nonlinearity of the magnetostrictive properties. The effect on sensor output is particularly pronounced in magnetoelastic and magnetoelectric composite devices, but the results generally apply to all sensor devices incorporating magnetic materials. Therefore, the identified magnetic noise source makes a significant contribution to understanding the limitations of magnetic sensors and provides important guidelines for optimizing future magnetic sensors for low detectivity.

Miniaturized double-wing ∆E-effect magnetic field sensors

“…Previous work on cantilever-type ΔE-effect sensors has demonstrated the detrimental influence of inhomogeneous effective magnetic properties around the clamping caused by shape anisotropy and residual stress 32 , 40 , 41 . Another persistent challenge connected to residual stress is reproducibility: huge device-to-device performance variations by more than 200% and resonance frequency deviations of 6–10% are reported for magnetoelectric resonators with identical dimensions caused by minimal stress that couples into the magnetic properties via the large magnetostriction 42 , 43 .…”

“…Hence, a magnetic field can alter the stiffness tensor of magnetostrictive materials and induce a shift in the resonance frequency [27][28][29][30][31][32] , which can be read out electrically 26 . ΔE-effect magnetic field sensors designed as plate and cantilever resonators and surface acoustic wave devices have demonstrated detection limits in the sub-nT regime at low frequencies < < 1 kHz 15,[33][34][35][36][37][38][39] .Previous work on cantilever-type ΔE-effect sensors has demonstrated the detrimental influence of inhomogeneous effective magnetic properties around the clamping caused by shape anisotropy and residual stress 32,40,41 . Another persistent challenge connected to residual stress is reproducibility: huge device-to-device performance variations by more than 200% and resonance frequency deviations of 6-10% are reported for magnetoelectric resonators with identical dimensions caused by minimal stress that couples into the magnetic properties via the large magnetostriction 42,43 .…”