Magnetic Noise in Magnetoelectric Magnetic Field Sensors

Intrinsic magnetic noise limits the performance of all magnetic field sensors based on magnetic films. Understanding the origins of magnetic noise and the factors influencing it is, therefore, crucial for advancing magnetic field sensor technology. This thesis presents a comprehensive study of noise mechanisms in magnetoelectric (ME) magnetic field sensors, focusing on two concepts: converse ME sensors and sensors exploiting the ΔE effect.

Signal and noise models were developed for both sensor types, linking material parameters, geometry, and operating conditions to performance. These models were validated experimentally, yielding several key insights. First, beyond thermal-magnetic noise, an additional noise source mediated by electromechanical excitation was identified as essential for describing multi-domain samples. A phenomenological expression for this carrier-mediated noise was derived and confirmed experimentally. The suppression of carrier-mediated noise was demonstrated to be possible through the engineering of the magnetic layer and domain configuration. Second, the work shows the critical influence of magnetoelastic nonlinearities. Experiments revealed that these nonlinearities enhance magnetic sensitivity through larger frequency detuning, but also introduce nonlinear magneto-mechanical losses, which were not previously recognized in ME sensors. Evidence further suggests that these losses underlie an additional noise mechanism, which is fundamentally tied to magnetoelasticity and may impose significant performance limits. Finally, a comparative analysis revealed distinct differences between the two concepts, along with the strong influence of the ΔE effect on the signal and bandwidth of converse ME sensors.

In summary, this thesis advances the fundamental understanding of magnetic noise in ME sensors and outlines strategies to improve their performance for modern applications.

Rights

Use and reproduction:


CC BY-SA 4.0

Please note that individual components of the publication may be subject to other licensing or copyright conditions.

Cite

Citation style:
Could not load citation form.