Impact of nitrogen on the charge-to-spin conversion efficiency in antiferromagnetic Mn3PtN compared to Mn3Pt thin films

The bilayer structures consisting of Mn₃PtN (5 nm)/CoFeB(3 nm) and Mn₃Pt(5 nm)/CoFeB(3 nm) were fabricated via magnetron sputtering to investigate the role of nitrogen on charge-to-spin conversion efficiency in the noncollinear antiferromagnets (AFMs). The crystal structure of Mn₃PtN (MPN) without N is consistent with that of Mn₃Pt (MP) with L1₂-ordered structure, which allows us to study the different charge-to-spin conversion efficiency for AFMs with and without N. The spin-torque ferromagnetic resonance and second-harmonic Hall measurements were performed for both samples. It was revealed that the spin Hall angle (θSH) of the MPN with spin polarization in the y direction was observed to be {~}0.033, exceeding the corresponding value of MP ({~}0.025), which was qualitatively supported by the first-principles calculation. These results led us to conclude that N plays a crucial role in stabilizing the noncolliear antiferromagnetic structure and creating an electronic state advantage for the enhanced θSH.