Hydrogen irradiation-induced magnetic phase transition modulation in FeRh films*

FeRh shows metamagnetic first-order phase transition from antiferromagnetic to ferromagnetic above 370 K. Also, it accompanies a volume expansion of about 1% and variation of electrical resistivity due to the increasing density-of-state at the Fermi level. To utilize phase transition characteristics for spintronics device applications, the transition temperature should be adjustable. Multiple methods such as doping, inducing interfacial strain, and forming various defect states have been attempted to modify the phase transition characteristics.

In this presentation, we applied the ex-situ method to modify the phase transition characteristics and results. The local defects were induced in FeRh thin films through hydrogen ion irradiation. As a result, it was observed that with the increase in hydrogen irradiation, the transition temperature decreased, and the initial residual-ferromagnetic state in the antiferromagnetic region increased due to the formation of Fe-Frenkel defects. Furthermore, DFT calculations confirmed that the Fe-Frenkel defect affected the breakdown of hybridization between Fe and Rh, resulting in the increased residual ferromagnetic state below the transition temperature and decreased the transition temperature.