Controlled spin-to-charge conversion in noncollinear antiferromagnet-based Py/Mn$_{3}$Pt heterostructure

Noncollinear antiferromagnets (NCAFs) have recently emerged as promising candidates for future spintronic technologies, offering ultrafast switching, negligible stray fields allowing dense packing, and robustness against external magnetic perturbations. When interfaced with ferromagnets (FMs), they can strongly influence interfacial exchange and spin-torque mechanisms that enable manipulating magnetic order and realizing functionalities beyond conventional heavy metals (HMs) based FM/HM heterostructures. Here, we perform a broadband ferromagnetic resonance (FMR) study to systematically investigate the magnetization dynamics and spin-to-charge conversion in permalloy (Py) and Mn$_3$Pt bilayers. High-quality Py films provide a well-defined FMR spectra with a low Gilbert damping parameter ( $α_{\mathrm{eff}} \approx 9.8 \times 10^{-3}$). We observe a pronounced enhancement of damping with intrinsic value $α_{\mathrm{int}} \approx 3.1 \times 10^{-2}$ in the Py/Mn$_3$Pt bilayer, indicating efficient spin pumping into the NCAF layer. Frequency dependent linewidth analysis shows a predominantly Gilbert type damping in the bilayers and the corresponding effective spin-mixing conductance ( $g^{\uparrow\downarrow}_{\mathrm{eff}} \approx 4.8 \times 10^{18}$m$^{-2}$) is comparable to that of other high-performance antiferromagnetic heterostructures. These results are significant for establishing NCAFs as a candidate material for spin generation and highlights the potential of Py/Mn$_3$Pt bilayers for efficient and ultrafast spintronic applications.