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Bandwidth-enhanced noise-suppressed current source enabled by a spin-exchange relaxation-free magnetometer

Tobias Menold1,2,*, Arianna Bertoluzza1, Patrick Hildebrand1,2, Ann-Kathrin Gottschalk1, Daniel Braun1, József Fortágh1, and Andreas Günther1,†

  • *Contact author: tobias.menold@ifsw.uni-stuttgart.de
  • †Contact author: a.guenther@uni-tuebingen.de
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Phys. Rev. Applied 26, 014042 – Published 14 July, 2026

DOI: https://doi.org/10.1103/3655-6w65

Abstract

This work investigates the behavior of a spin-exchange relaxation-free magnetometer integrated into the feedback branch of a closed-loop control circuit, designed to realize a noise-suppressed current source. In this configuration, the magnetometer bandwidth is enhanced by almost 2 orders of magnitude as compared to the open-loop setup. Incorporating an injection transformer, the proposed system effectively reduces current noise to below 3  nA/Hz over a broad frequency bandwidth, independent of dc-current offsets. Analysis of the system sensitivity reveals the performance to be currently limited by technical noise. If this were to be eliminated, the system would achieve a current-sensing sensitivity on the order of a few pA/Hz while maintaining perfect galvanic isolation from the target circuit.

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Phys. Rev. Applied 26, 014042– Published 14 July, 2026
  • Received 2 July 2025
  • Revised 31 March 2026
  • Accepted 20 May 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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