Using optically pumped magnetometers to identify initial damage in bulk material during fatigue testing

The extreme sensitivity of quantum magnetometers enables new applications in material testing such as the identification of single defect events in the bulk of small volume specimen (0.1 mm³). Exposing ferromagnetic materials to strain alters their magnetic response. Due to uncompensated spins, defects arising from the fatigue process interact with magnetic domain walls. Optically pumped zero-field magnetometers (OPM) provide the sensitivity required to measure small variations in the magnetic response and potentially to quantify damage in the material. We provide first results of a novel micro fatigue setup with an integrated OPM to correlate variations of the magnetic response in a multimodal approach. The position of the Villari reversals within the magneto-mechanic hysteresis and the amplitude of magnetic field are potential candidates to estimate fatigue damage within the specimen.