We report on a broadband search for axionlike particle (ALP) interactions using a radio-frequency operated ${}^{87}\mathrm{Rb}$ atomic magnetometer. The instrument provides wide spectral coverage and sensitivity to an oscillating pseudomagnetic field that may be generated by the gradient coupling of the ALP field to the constituent fermions of atoms. We search for an ALP-gradient signature in the mass range $2.40\times {10}^{-10}\mathrm{eV}/c^2–2.11\times {10}^{-9}\mathrm{eV}/c^2$. No statistically significant signatures of an oscillating magnetic field are observed, and we derive upper limits on the corresponding ALP-proton, -neutron, and -electron couplings, $g_{\alpha pp}$, $g_{\alpha nn}$, and $g_{\alpha ee}$, respectively. The result on $g_{\alpha pp}$ improves over previous laboratory searches, while the limits on $g_{\alpha nn}$ and $g_{\alpha ee}$ complement earlier laboratory searches and astrophysical bounds. The work extends searches for ALP-fermion interactions into a mass region largely unexplored in a dark matter context, demonstrating the potential of our method for broadband axionlike particle searches targeting the Galactic dark matter halo.

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• Dark matter
• Magnetometry
• Axion-like particles