Sensitivity enhancement for a light axion dark matter search with magnetic material

TL;DR

This paper proposes using permeable magnetic materials to enhance static magnetic fields, significantly improving the sensitivity of low-frequency axion dark matter searches, demonstrated with gadolinium iron garnet toroids.

Contribution

The study introduces a method to increase magnetic field strength in axion searches using permeable materials, achieving a fourfold enhancement and demonstrating practical sensitivity improvements.

Findings

Fourfold magnetic field enhancement with gadolinium iron garnet toroids.

Sensitivity to axion-photon coupling of ~10^{-9} GeV^{-1} after 8 hours.

Effective systematics rejection via signal correlation from multiple toroids.

Abstract

The sensitivity of experimental searches for axion dark matter coupled to photons is typically proportional to the strength of the applied static magnetic field. We demonstrate how a permeable material can be used to enhance the magnitude of this static magnetic field, and therefore improve the sensitivity of such searches in the low frequency lumped-circuit limit. Using gadolinium iron garnet toroids at temperature 4.2 K results in a factor of 4 enhancement compared to an air-core toroidal design. The enhancement is limited by magnetic saturation. Correlation of signals from three such toroids allows efficient rejection of systematics due to electromagnetic interference. The sensitivity of a centimeter-scale axion dark matter search based on this approach is on the order of $g_{a\gamma\gamma}\approx10^{-9}$ GeV$^{-1}$ after 8 hours of data collection for axion masses near $10^{-10}$ eV. This approach may substantially extend the sensitivity reach of large-volume lumped element axion dark matter searches.