Ultrashort Spin Waves Emission by an Antiferromagnetic Domain Wall Driven by Spin Current

Antiferromagnets (AFMs) have great benefits for spintronic applications [1] such as high frequencies (up to THz) [2], high speeds (up to tens of km/s) of magnetic excitations, and field-free operation. Advanced devices will require high-speed propagating spin waves (SWs) as signal carriers, i.e. SWs with high k-vectors, the excitations of which remain challenging.

We show that a domain wall (DW) in AFM with an anisotropy or DMI, driven by spin current, can be a source of such propagating SWs with high frequencies and shorter wavelengths, comparable to the exchange length of the AFM. In the proposed generator, the spin current, with polarization directed along the principal crystal axis, excites the precession of the Néel vector within the DW. The threshold current is defined by the value of the in-plane anisotropy, and the frequency of the DW precession is tuneable by the strength of the spin current. We show that the above precession of the DW leads to robust emission of high-frequency propagating SWs into the AFM strip with very short wavelengths comparable to the exchange length, which is hard to achieve by any other method.

[1] O. Gomonay et al., Nat. Physics 14, 213 (2018)

[2] R. Khymyn et al., Sci. Rep. 7, 43705 (2017); O. Sulymenko et al., Phys. Rev. Appl. 8, 064007 (2017)