Axions are a compelling dark matter candidate suggested by theories beyond the standard model. The predicted axion-electron coupling and the resulting pseudomagnetic field allow for laboratory axion searches. Here we report an experimental axion search via a superconductor-spin hybrid magnetometer. A state-of-the-art broadband magnetometer with a sensitivity of sub-$100\mathrm{a}\mathrm{T}/{\mathrm{Hz}}^{1/2}$ at tens of kHz has been realized by coupling a ferrite spin sensor to a readout system based on a superconducting quantum interference device. The most stringent terrestrial constraints on the axion-electron coupling have been established in the frequency range $5\sim 60\mathrm{kHz}$. In the future, an improvement on the constraints of more than 3 orders of magnitude is foreseeable through arrays of superconductor-spin hybrid magnetometers with optimized designs. This Letter demonstrates the potential of superconductor-spin hybrid magnetometers in high-precision magnetic field sensing and the study of fundamental physics.

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• Particle astrophysics
• Particle dark matter
• Axion-like particles
• Superconducting devices
• Dark matter detectors