Magnetic Evolution of the \textless 100\textgreater\ Interstitial Loop Formation Process in bcc Iron*

Interstitial loops are a signature of radiation damage in materials and are only observed in systems far from equilibrium state due to their high formation energies (approximately 4eV). Unlike other bcc metals, in which the interstitial loops are almost exclusively $\frac{1}{2}$ \textless 111\textgreater\ type, two types of loops, \textless 100\textgreater and $\frac{1}{2}$ \textless 111\textgreater\, are identified in bcc iron. Although $\frac{1}{2}$ \textless 111\textgreater\ loops can be formed directly by atomic displacment cascades, the mechanism of \textless 100\textgreater\ loop formation had remained undetermined since they were observed fifty years ago. Recently, the formation mechanism has been discovered using self-evolving atomistic kinetic Monte Carlo (SEAKMC) simulations. Here we describe the influence of magnetism in the corresponding loop formation process using the \textit{ab initio} locally self-consistent multiple-scattering (LSMS) method. Significant magnetic moment changes during the loop formation process are observed and their effect on the loop stability are evaluated. In addition, the effects of \textless 100\textgreater\ loop formation on the microstructural evolution and material properties will be discussed.