Large inverse spin Hall effect in the antiferromagnetic metal ${\mathrm{Ir}}_{20}$${\mathrm{Mn}}_{80}$

A spin current is usually detected by converting it into a charge current through the inverse spin Hall effect (ISHE) in thin layers of a nonmagnetic metal with large spin-orbit coupling, such as Pt, Pd, and Ta. Here we demonstrate that ${\mathrm{Ir}}_{20}$${\mathrm{Mn}}_{80}$, a high-temperature antiferromagnetic metal that is commonly employed in spin-valve devices, exhibits a large inverse spin Hall effect, as recently predicted theoretically. We present results of experiments in which the spin currents are generated either by microwave spin pumping or by the spin Seebeck effect in bilayers of singe-crystal yttrium iron garnet (YIG)/${\mathrm{Ir}}_{20}$${\mathrm{Mn}}_{80}$ and compare them with measurements in YIG/Pt bilayers. The results of both measurements are consistent, showing that ${\mathrm{Ir}}_{20}$${\mathrm{Mn}}_{80}$ has a spin Hall angle similar to Pt, and that it is an efficient spin-current detector.

Figure 1

Sketches showing the YIG/IrMn or YIG/Pt structures and the electrodes used to measure the dc voltage due to the ISHE charge current in the metallic layer resulting from the spin currents generated in two configurations: (a) microwave FMR spin pumping and (b) longitudinal spin Seebeck effect. The static field $H$ is applied in the film plane at an arbitrary angle with the sample edge.

Figure 2

(a), (b), and (c) Field scan microwave FMR absorption derivative spectra at a frequency 9.4 GHz of 6 μm thick YIG film with lateral dimensions 1.5 × 3.0 mm${}^2$ with the magnetic field applied in the film plane normal to the long dimension. In (a) the YIG film is bare while in (b) and (c) it is covered, respectively, with Pt (4 nm) and IrMn (5 nm). (d) Magneto-optical Kerr Effect (MOKE) magnetometry hysteresis loop of Py measured in Si(100)/Cu(8 nm)/Py(4 nm)/IrMn(4 nm) exhibiting the exchange bias effect produced by the AF arrangement of IrMn.

Figure 3

Field scan of the spin-pumping-ISHE voltage produced by FMR microwave excitation at a frequency 9.4 GHz in bilayers of YIG(6 μm)/IrMn(5 nm) in (a) and YIG(6 μm)/Pt(4 nm) in (b). The measurements in (a) and (b) were done with a shortened waveguide and input power 80 mW. The inset in (a) shows a sketch of the electrodes and connections used to measure the dc voltage in the metal layer, with the static field $H$ in the film plane at an angle $\varphi$ with the sample axis.

Figure 4

Variation of the ISHE voltage created by the longitudinal spin Seebeck effect with the temperature difference Δ$T$ between the two sides of the samples under a magnetic field with intensity $H$ applied in the plane transversely to the direction of the measured voltage. (a) and (c) Voltage as a function of $H$ for YIG/IrMn and YIG/Pt for various values of Δ$T$. (b) and (d) Voltage as function of Δ$T$ for $H$ = 1.0 kOe in both directions. The inset in (a) shows the sketch of the GGG/YIG/ML sample mount with the Peltier module used to apply the temperature difference and the electrodes used to measure the dc voltage.