Project A10 - Magnetic Noise of Magnetoelectric Sensors

A detailed understanding of magnetic noise behavior in magnetoelectric (ME) sensor structures is of fundamental interest for the realization of magnetic field sensors with ultra-low detection limits, as many promising sensor approaches of the CRC are presently limited in their performance due to magnetic noise. The aim of this project is to comprehend and quantify the influence of geometrical and physical imperfections as well as the connected magnetic microstructure on the magnetic noise of ME sensors. Defects of magnetic relevance include physical and geometrical deviations, which differentiate the real system from an idealized one. The nucleation and the behavior of magnetic domains and domain walls are highly related to the defect structure of the system. Examples of imperfections are local geometrical errors, non-uniform magnetic material properties, and local eigenstresses, all of which will influence the magnetic structure of the magnetic layers and its ME response characteristics.

To achieve the aforementioned goal, dedicated experimental methods, for example, time-resolved in-situ magneto-optical magnetic domain response analysis and local noise measurements, will be combined with high-resolved and adaptive micromagnetomechanical simulations including adaptive discretization approaches and scale transition methods. For the modelling, transfer functions will be derived, revealing the influence of geometrical and physical imperfections on the measured noise. The influence of material properties, sensor designs, and fabrication processes will be investigated numerically and experimentally. Different ME sensor concepts under consideration within the CRC (electrically modulated, surface acoustic wave, and soft composite-based sensors) will be covered in combination with magnetic domain, general magnetic, and noise investigations on well-defined model structures exhibiting artificial imperfections and tailored micromagnetic features. Our strategy will permit achieving accurate and direct insights into the exact influence of imperfections on the magnetic domain behavior and thus the magnetic noise. From comparing the results, a fundamental understanding of the role of different scales in time, depending on the operational frequency, and space will be developed. From the relevance to the magnetic noise behavior, we will derive targeted strategies for noise reduction as well as identify possible feasibility limits.

Involved Researchers

Person		Role
	Prof. Dr. Jeffrey McCord Materials Science Nanoscale Magnetic Materials	Project lead
	Dr.-Ing. Stephan Wulfinghoff Materials Science Computational Materials Science	Project lead
	M.Sc. Christian Dorn Materials Science Computational Materials Science	Doctoral researcher
	M.Sc. Elizaveta Spetzler Materials Science Nanoscale Magnetic Materials - Magnetic Domains	Doctoral researcher

Role within the Collaborative Research Centre

The global objective of our project is the research on the relevance and quantification of micromagnetic activity, contributing to the performance of the individual, pursued sensor concepts in research area A. Thereby, A10 plays a central role within the CRC to guide sensor concepts. We will strongly cooperate in sample preparation with project Z1 and A1. On magnetic noise characterization we will cooperate with B1 and Z2. A10 will further contribute to the focus groups “Modelling”, “ME Sensors”, “Concepts based on E effect”, and “Magnetic layers”. The doctoral researchers will be active in the IRTG. Collaborations with the following projects are planned:

Project-related Publications

F. Ilgaz, E. Spetzler, P. Wiegand, F. Faupel, R. Rieger, J. McCord, B. Spetzler: Miniaturized Double-Wing ∆E-Effect Magnetic Field Sensors, Scientific Reports, vol. 14, no. 11075, 2024.

C. Dorn, S. Wulfinghoff: A Magneto-Mechanically Coupled Material Model for Magnetic Sensor Investigation, Proc. Appl. Math. Mech., vol. 22, no. 1, e202200008, 2023.

S. Wulfinghoff, C. Dorn:  A Continuum Theory for Stripe-Shaped Magnetic Domains in Thin Films, J. Magn. Magn. Mater., Dec., 588, 171375, 2023.

E. Spetzler, B. Spetzler, J. McCord: A Magnetoelastic Twist on Magnetic Noise: The Connection with Intrinsic Nonlinearities, Advanced Functional Materials, no. 2309867, 2023.

C. Dorn, M. Hörsting, S. Wulfinghoff: Computing Barkhausen Noise Spectra for Magnetostrictive Thin Film Composites Using Efficient Magnetization-magnitude Preserving Simulation Techniques, Journal of Applied Physics, 134. Jg., no. 13, 2023.

G. Masciocchi, M. Fattouhi, E. Spetzler, M.-A. Syskaki, R. Lehndorff, E. Martinez, J. McCord, L. Lopez-Diaz, A. Kehlberger, M. Kläui: Generation of Imprinted Strain Gradients for Spintronics, Applied Physics Letters, 123, 022404, 2023.

J. Schmalz, E. Spetzler, J. McCord, M. Gerken: Investigation of Unwanted Oscillations of Electrically Modulated Magnetoelectric Cantilever Sensors, MDPI Sensors, no. 11, issue 11, pp. 5012, 2023.

C. Dorn, S. Wulfinghoff: Computational Micro-Magneto-Mechanics – Application to Thin Film Composites, ECCOMAS Congress 2022, 8th European Congress on Computational Methods in Applied Sciences and Engineering, 2023.

C. Dorn, S. Wulfinghoff: Computing Magnetic Noise With Micro-Magneto-Mechanical Simulations, IEEE Transactions on Magnetics, vol. 59, no. 2, pp. 1-4, Feb. 2023.

R. Schäfer, J. McCord:  Magneto-Optical Microscopy, in Magnetic measurement techniques for materials characterization, 171-229, Springer, 2023.

C. Müller, P. Durdaut, R. B. Holländer, A. Kittmann, V. Schell, D. Meyners, M. Höft, E. Quandt, J. McCord: Imaging of Love Waves and Their Interaction with Magnetic Domain Walls in Magnetoelectric Magnetic Field Sensors, Advanced Electronic Materials, 2200033, 2022.