All-electrical manipulation of magnetization dynamics in a ferromagnet by antiferromagnets with anisotropic spin Hall effects

We investigate spin-orbit torques of metallic CuAu-I-type antiferromagnets using spin-torque ferromagnetic resonance tuned by a dc-bias current. The observed spin torques predominantly arise from diffusive transport of spin current generated by the spin Hall effect. We find a growth-orientation dependence of the spin torques by studying epitaxial samples, which may be correlated to the anisotropy of the spin Hall effect. The observed anisotropy is consistent with first-principles calculations on the intrinsic spin Hall effect. Our work demonstrates large tunable spin-orbit effects in magnetically ordered materials.

Figure 1

(a) Schematic illustration of the spin-Hall-effect-induced spin transfer torques (${\tau }_{\left|\right|}$ and ${\tau }_{\perp }$) of AF/Cu/Py multilayers. (b) Depiction of the circuit used for the spin-torque ferromagnetic resonance measurement and the sample contact geometry. (c) Comparison of resistance change due to heating caused by dc and rf currents.

Figure 2

Measured spin-torque ferromagnetic resonance signals from AF(10)/Cu(1)/Py(5) at room temperature.

Figure 3

(a) Resonance field versus frequency and the corresponding Kittel fit for different antiferromagnetic sample stacks. (b) and (c) Resonance linewidth ($\mathrm{\Delta }H$) versus dc-bias current ($I_{\mathrm{dc}}$) at different frequencies, $f=4$, 5, and 6 GHz [dc current polarity: solid (+), empty (-)], and resonance linewidth versus frequency at different dc-bias currents, $I_{\mathrm{dc}}=-2$, 0, and 2 mA, for PtMn(10)/Py(5).

Figure 4

(a,c,e) Resonance linewidth and (b,d,f) resonance field versus dc-bias current at 5 GHz for 5-$\mu \mathrm{m}$-wide PtMn/Cu/Py, IrMn/Cu/Py, and PdMn/Cu/Py devices. Linear fitting for the dc-current effect is shown for PtMn. The calculated Oersted field contribution is indicated by the dashed line in panel (b).

Figure 5

(a) A sketch illustrating the chemical structure of CuAu-I-type antiferromagnets grown along (001)[$c$-axis normal] and (100)[$a$-axis normal] directions, and (b) their corresponding x-ray diffraction patterns. The principal axes are inequivalent ($c \ne a$) for PtMn, IrMn, and PdMn except for FeMn ($c$ = $a$).

Figure 6

Measured spin-torque ferromagnetic resonance signals from (a) $a$- and (b) $c$-axis PtMn(10)/Cu(1)/Py(5), and (c,d) the corresponding resonance linewidth versus dc-bias current at 5 GHz.