Magnetically induced noise is one of the major contributors to the limits of magnetically driven sensors. Main noise sources are domain wall movement and related abrupt irreversible magnetization changes . To hinder these formations, specialized techniques such as exchange bias (EB) have been utilized . However, the concepts were insufficient in reducing the magnetic noise contribution within composite magnetoelectric sensors .
We present a novel concept utilizing EB multilayer systems with interchangeable antiparallel alignment of magnetization in neighboring magnetic layers. We show stable magnetic domain configurations with negligible irreversible changes of magnetization during the operation of the sensors. Induction measurements specify a linear response of magnetization up to magnetic fields of 1 mT in amplitude and a very weak transversal signal. This indicates high purity of opposing coherent rotation of magnetization in the individual layers. Investigations with static and time-resolved magneto-optical Kerr microscopy  in the working frequency of the sensors confirm the findings. With electrical measurements, the magnetic noise impact was evaluated with operation of the sensor at 10 Hz using magnetic frequency conversion (MFC) . The sensors yield a significant improvement of the noise threshold compared to previous-generation sensors. Even with the application of MFC, the developed sensors reach noise levels limited by the thermo-mechanical noise. The results represent an important breakthrough for the development of magnetoelectric sensors as well as other sensors that utilize magnetic layers for their operation.
The results were obtained within the Collaborative Research Centre SFB 1261, funded by the German Science foundation (DFG).
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