Large spin Hall angle in MnPt-based antiferromagnetic alloys

Antiferromagnets (AFMs) have emerged as crucial materials for spintronic technologies for their ability to host spin-dependent transport phenomena, despite their zero net magnetization. Their robustness against external magnetic fields and ultrafast spin dynamics make them ideal for efficient spin-charge interconversion. However, unlike ferromagnets, many details of spin transport mechanisms in AFMs remain unexplored. In this study, we theoretically investigate the enhancement of the spin Hall effect in AFM materials, with a focus on Mn-based binary alloys. By alloying MnPt with Ir ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>MnPt</a:mi> <a:mi>x</a:mi> </a:msub> <a:msub> <a:mi>Ir</a:mi> <a:mrow> <a:mn>1</a:mn> <a:mo>−</a:mo> <a:mi>x</a:mi> </a:mrow> </a:msub> </a:mrow> </a:math> ) or Pd ( <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:msub> <b:mtext>MnPt</b:mtext> <b:mi>x</b:mi> </b:msub> <b:msub> <b:mtext>Pd</b:mtext> <b:mrow> <b:mn>1</b:mn> <b:mo>−</b:mo> <b:mi>x</b:mi> </b:mrow> </b:msub> </b:mrow> </b:math> ), we aim to elucidate the impact of tuning the Fermi energy and of changing the spin-orbit coupling strength on the spin Hall conductivity, and ultimately on the spin Hall angle (SHA). We show that lightly doping MnPt with Ir enhances the SHA from approximately 3% in pristine MnPt, as experimentally reported at room temperature, to nearly 12% under the same conditions. Building on these findings, we employ density-of-states and band-structure analyses to unravel the microscopic origin of this enhancement. Overall, our results highlight the potential of antiferromagnetic alloys for efficient spin-current generation and underscore their promise for advancing spintronic applications.