Abstract
The electrical control of antiferromagnetic moments is a key technological goal of antiferromagnet-based spintronics, which promises favourable device characteristics such as ultrafast operation and high-density integration as compared to conventional ferromagnet-based devices. To date, the manipulation of antiferromagnetic moments by electric current has been demonstrated in epitaxial antiferromagnets with broken inversion symmetry or antiferromagnets interfaced with a heavy metal, in which spin-orbit torque (SOT) drives the antiferromagnetic domain wall. Here, we report current-induced manipulation of the exchange bias in IrMn/NiFe bilayers without a heavy metal. We show that the direction of the exchange bias is gradually modulated up to ±22 degrees by an in-plane current, which is independent of the NiFe thickness. This suggests that spin currents arising in the IrMn layer exert SOTs on uncompensated antiferromagnetic moments at the interface which then rotate the antiferromagnetic moments. Furthermore, the memristive features are preserved in sub-micron devices, facilitating nanoscale multi-level antiferromagnetic spintronic devices.
Highlights
The electrical control of antiferromagnetic moments is a key technological goal of antiferromagnet-based spintronics, which promises favourable device characteristics such as ultrafast operation and high-density integration as compared to conventional ferromagnetbased devices
To understand the switching mechanism, we investigate the dependence of the rotation angle of the exchange bias on the IrMn and NiFe thicknesses; φEB diminishes with an increase in the IrMn thickness, indicating that the spin-orbit torque (SOT)-induced rotation of the exchange bias is hindered by the AFM anisotropy energy, which increases with its thickness
We further investigate whether the change in the RH value reflects the rotation of the exchange bias of IrMn, given that the RH value of the IrMn/NiFe bilayer is mostly dominated by NiFe (Supplementary Note 3)
Summary
The electrical control of antiferromagnetic moments is a key technological goal of antiferromagnet-based spintronics, which promises favourable device characteristics such as ultrafast operation and high-density integration as compared to conventional ferromagnetbased devices. We show that the direction of the exchange bias is gradually modulated up to ±22 degrees by an in-plane current, which is independent of the NiFe thickness This suggests that spin currents arising in the IrMn layer exert SOTs on uncompensated antiferromagnetic moments at the interface which rotate the antiferromagnetic moments. The first is to employ a single AFM layer with spatial broken inversion symmetry such as CuMnAs9–11 or Mn2Au12–15 In these materials, electric currents locally induce nonequilibrium spin polarization, generating Néel spin–orbit torque (SOT) with opposite signs for each sub-lattice with opposite magnetic moments[16]. We observe that the planar Hall resistance of the bilayer is gradually modulated by an in-plane current and retains its value even after turning off the current This demonstrates that the SOT caused by the spin Hall effect in IrMn effectively controls the exchange bias direction in a range of ±22°. We show that the reversible memristive features of the SOT-induced AFM switching are maintained in a 500-nm-sized device, offering a route for developing nanoscale AFM spintronics devices for applications in neuromorphic computing
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