Slow Neutron Polarimetry for a Spin-Dependent Fifth Force Search in Terbium Iron Garnet: Advanced Data Analysis Techniques*

Rare-earth iron garnets exhibit a temperature-dependent orbital cancellation of magnetism linked to electron spins, resulting in a dense ensemble of polarized electrons with (ideally) zero magnetization. The NSR-Ferrimagnets Collaboration has conducted experiments utilizing spin echo spectroscopy and neutron imaging techniques to search for exotic spin-dependent neutron-electron interactions in the polycrystalline ferrimagnet terbium iron garnet Tb₃Fe₅O₁₂ at the compensation temperature T_c. This is performed by characterizing a spin-state asymmetry within a large set of neutron imaging data. We will present advanced techniques to account for systematic effects including external time-dependent magnetic field shifts as well as preliminary results from the June 2024 experiment at the HFIR CG-1D neutron imaging beamline at ORNL.