Investigating the mechanism of magnetic phase transition temperature of FeRh thin films by doping copper impurities

Abstract In this work, we study the magnetic phase transition (from antiferromagnetic (AFM) to ferromagnetic (FM) states) temperature (TAFM-FM) of iron-rhodium (FeRh) thin films and its tuning by doping copper impurities up to 4.5 at.%. The thin epitaxial FeRh films are prepared by DC magnetron sputtering on the MgO (001) substrate and the doping is performed by simultaneously co-sputtering Cu impurities. More importantly, the doping of Cu impurities drastically decreases the TAFM-FM of FeRh films by more than 100 K, which cannot be precisely described either by strain measurement or change in the valence electron concentration as published by previous works. To explain this unique phenomenon, we proposed a hypothesis to determine the reduction of long-range order of AFM and correlated the change in transition temperature exponentially as a function of doping different concentrations of Cu impurities. Overall, this study concludes that lattice strain, valence electrons per atom, existence of mixed phase and short range order of AFM altogether attribute to the significant decrease of the TAFM-FM.