Correlation between phase transition characteristics and hydrogen irradiation-induced Frenkel defect formations in FeRh films

FeRh films exhibit an extraordinary magnetic phase transition accompanied by structural and electrical variations. This study intentionally modified the local atomic environment using hydrogen irradiation to elucidate the transition characteristics. It was observed that with the increase in hydrogen irradiation, the initial residual-ferromagnetic state in the antiferromagnetic region (i.e., below the magnetic phase transition temperature) increased. In addition, the transition temperature decreased. Structural and chemical analysis revealed that the increased hydrogen irradiation enhanced local structural distortion and Fe-Frenkel defect formation. Furthermore, density functional theory calculations confirmed that the Fe-Frenkel defect affected the breakdown of hybridization between Fe and Rh. Therefore, it caused the increased residual ferromagnetic state below the transition temperature and decreased the transition temperature.