Nearly full magnetization recovery after a strong collision between Fe nanoparticles

The magnetic history of extraterrestrial materials, such as meteorites, is a critical archive for understanding solar system processes. However, the effect of hypervelocity collisions on this record remains poorly understood, particularly whether such events can erase or reset magnetization through heating or pressure-induced phase transformations. Using spin-lattice dynamics simulations, we investigate collisions between nanoscale iron particles (10–20 nm diameter) at velocities of 1–2 km s − 1 , explicitly modeling magnetic interactions. Our results show that while collisions at 2 km s − 1 generate pressures sufficient to induce local melting and a limited, transient nonmagnetic hexagonal close-packed (hcp) phase, the primary magnetic effect is global heating above the Curie temperature, transitioning the particles to a paramagnetic state. The particles form a single nanoparticle after the impact, with some twins, dislocations, and point defects. Unlike under bulk single-crystal loading, several nanograins are formed. Upon simulated cooling, emulating radiative cooling, the now-joined particles consistently recover a strong, single-domain ferromagnetic state, irrespective of their initial magnetic-domain orientation or the resulting microstructural defects. The final ferromagnetic state does not preserve a memory of the pre-impact magnetic configuration. These findings demonstrate that a strong ferromagnetic signature in recovered nanoscale iron does not preclude a history of severe hypervelocity collisions, with significant implications for the interpretation of magnetic records in asteroidal and meteoritic materials.