Enhancing antiferromagnetic anisotropic magnetoresistance by substitutional doping

The study of the anisotropic magnetoresistance (AMR) in antiferromagnetic materials is essential due to their superior properties, which have led to a broader application of antiferromagnets in spintronic devices. In this work, we examine the impact of substitutional doping on the antiferromagnetic AMR of $\mathrm{Fe}\mathrm{Rh}$. We discover that $\mathrm{Pt}$-$\mathrm{Rh}$ substitution can markedly enhance the antiferromagnetic AMR of $\mathrm{Fe}\mathrm{Rh}$. With a 7.7% $\mathrm{Pt}$-$\mathrm{Rh}$ substitution, the AMR increases up to fivefold compared to that of pristine $\mathrm{Fe}\mathrm{Rh}$ films. Conversely, $\mathrm{Mn}$-$\mathrm{Fe}$ substitution results in a decrease in the antiferromagnetic AMR of $\mathrm{Fe}\mathrm{Rh}$. First-principles calculations are employed to comprehend the distinct effects of the substitution on the electronic band structures. Compared to the $\mathrm{Mn}$-$\mathrm{Fe}$ substitution, the $\mathrm{Pt}$-$\mathrm{Rh}$ substitution leads to a greater difference in electrical transport between parallel and perpendicular orientations, culminating in a larger AMR. This is because the replacement with $\mathrm{Pt}$-$\mathrm{Rh}$ increases the spin-orbit coupling interaction and s-d scattering in the system, whereas the substitution with $\mathrm{Mn}$-$\mathrm{Fe}$ reduces the spin-orbit coupling. Our research offers valuable insights into the underlying mechanisms controlling the AMR in antiferromagnetic materials and establishes a foundation for further enhancing their functionality.