Particle Detection Using Magnetic Avalanche in Single-Molecule Magnet Crystals

A relatively unexplored region in the Dark Matter (DM) search is the meV-MeV range. Several promising candidates lie in this region including light-mass DM (keV-MeV) and “dark photons” (meV-eV). A low threshold detector probing to the meV range has been proposed utilizing single-molecule magnets (SMMs) and the phenomenon called magnetic avalanche. SMMs are self-contained, high-spin molecules whose magnetic potential can be described with a double well potential. At low temperatures (often cryogenic), this potential shifts creating a metastable state. The parameters can be adjusted such that a small energy will move a molecule from the metastable state into the ground state, releasing energy in the process. The released energy allows neighboring molecules to repeat the process across the full crystal. This phenomenon is called magnetic avalanche and is key for our proposed low-threshold detector. 

In this talk, I present the first results of particle-induced magnetic avalanches in the SMM Mn12-ac and subsequent results in the SMM Fe8. While the Mn12-ac experiments could only confirm an energy threshold in the MeV range, Fe8 experiments resulted in an energy threshold in the keV range, showing several orders of magnitude in improvement. Dozens of other SMMs have been discovered since the original discovery of Mn12-ac in 1993 with a wide range of parameters making it possible to create a detector in the meV range, leading to a new generation of competitive DM detectors.