Impact of nitrogen on the charge-to-spin conversion efficiency in antiferromagnetic ${\mathrm{Mn}}_{3}\mathrm{PtN}$ compared to ${\mathrm{Mn}}_{3}\mathrm{Pt}$ thin films (2024)

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  Figure 1

  (a) Unit cell of ${\mathrm{Mn}}_3\mathrm{PtN}$ (MPN) crystal with antiperovskite structure together with the possible ${\mathrm{\Gamma }}_{4g}$-type magnetic structure. (b) Out-of-plane XRD profile for the stacking of MgOsub./MPN(5)/CoFeB(3)/MgO(2) (in nm). The dashed lines represent the fitting curves with pseudo-Voit function to estimate the degree of order (S). Inset shows an atomic force microscopy image of the 25-nm-thick MPN surface. (c), (d) The same as 1(a) and 1(b), but regarding the ${\mathrm{Mn}}_3\mathrm{Pt}$ (MP).

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  Figure 2

  (a), (b) Magnetic hysteresis (solid circles) and anomalous Hall resistivity (${\rho }_{xy}$) (open triangles) for the 5-nm-thick MPN (a) and the 5-nm-thick MP single layers (b) as a function of the out-of-plane magnetic field ($H_{\mathrm{perp}}$) at room temperature. (c) Magnetic hysteresis for the stacking of MgOsub./MPN(5)/CFB(3)/MgO(2) (red) and that of MgO sub./MP(5)/CFB(3)/MgO(2) (blue) (in nm) as a function of in-plane magnetic field ($H_{\mathrm{inp}}$) at room temperature. The inset represents the enlarged magnetic hysteresis loops near the zero field.

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  Figure 3

  (a) Spin-torque ferromagnetic resonance (ST-FMR) setups together with the typical field-domain spectrum ($V_{\mathrm{mix}}$) recorded at the in-plane magnetic field (H) with the azimuthal angle of φ = 45 °. The blue and green solid lines represent the Lorentzian and anti-Lorentzian fitting results using Eq.(3), respectively. (b), (c) Relationship between the resonance field ($H_{\mathrm{r}}$) and the applied rf frequency ($f$) (b), and the $f$ and ST-FMR linewidth (ΔH) (c) for both MgOsub./MPN(5)/CFB(3)/MgO(2) and MgOsub./MP(5)/CFB(3)/MgO(2) (in nanometers). (d), (e) φ dependence of symmetric Lorentzian ($V_{\mathrm{s}}$) and antisymmetric Lorentzian ($V_{\mathrm{a}}$) components for the same samples. The solid and dashed lines represent the fitting curve using Eqs.(6) and(7), respectively. (f), (g) Dependences of spin Hall angles (${\theta }_{\mathrm{SH}}$) on $f$ (f) and the thickness of MPN and MP layers (g) estimated using Eq.(8), which is dominated by the spin torque originating from the polarization in $y$ direction.

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  Figure 4

  (a) Measurement configuration of the second-harmonic Hall voltage. (b) Electric conductance as a function of the CoFeB layer thickness ($d_{\mathrm{CFB}}$). The dashed lines represent the fitting results using the formula $R_{xx}^{-1}\left(\frac{L}{W}\right)=\frac{d_{\mathrm{CFB}}}{{\rho }_{xx}^{\mathrm{CFB}}}+\frac{d_{\mathrm{AFM}}}{{\rho }_{xx}^{\mathrm{AFM}}}$. (c), (d) Second-harmonic Hall voltage ($V_{xy}^{2\omega }$) as a function of azimuthal angle of in-plane field (φ) with $I_{\mathrm{ac}}=2$ mA and $H_{\mathrm{ext}}=50$ mT. Solid and dashed lines represent the fitting results by Eqs.(9, 10, 11). (e), (f) Fitting parameter |A| under the various H, where $H_{\mathrm{k}}$ represents the anisotropy field evaluated by AHE (see Fig. S4 in Supplemental Material[51]). Dashed lines represent the linear fit to the plots for higher H region to obtain the $H_{\mathrm{DL}}$ as shown by Eq.(10).

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  Figure 5

  (a)–(c) Calculated spin Hall conductivities for MP and MPN ${\sigma }_{\alpha \beta }^{\gamma }$ as a function of energy (E) relative to the Fermi level ($E_{\mathrm{F}}$), where $\alpha$, $\beta$, and $\gamma$ are the direction of current flow, the direction of spin current, and the polarization direction of the spin (spin quantum axis), respectively. (d) Spin Berry curvature at the $E_{\mathrm{F}}$ along the high-symmetry line in the first Brillouin zone for ${\mathrm{Mn}}_3\mathrm{Pt}$ and ${\mathrm{Mn}}_3\mathrm{PtN}$. (e), (f) Projections of each atomic orbital on the band dispersions of ${\mathrm{Mn}}_3\mathrm{Pt}$ and ${\mathrm{Mn}}_3\mathrm{PtN}$ along high-symmetry line around the $E_{\mathrm{F}}$. The projections on N orbitals are magnified by a factor of 3 compared to other atomic orbitals. The high-symmetry $k$ points $\left(x,y,z\right)$ are $\mathrm{\Gamma }\left(0,0,0\right)$, $X\left(0,1/2,0\right)$ $M\left(1/2,1/2,0\right)$, $A\left(1/2,1/2,1/2\right)$, $Z\left(0,0,1/2\right)$, $\mathrm{and}R\left(0,1/2,1/2\right)$ in the Brillouin zone $x{\mathit{b}}_1+y{\mathit{b}}_2+z{\mathit{b}}_3$, respectively. The ${\mathit{b}}_1,{\mathit{b}}_2,{\mathit{b}}_3$ are the reciprocal vectors of the tetragonal cell.

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