Antiferromagnetic Bloch line driven by spin current - an analog of a fluxon in a long Josephson junction

Antiferromagnets (AFMs) are promising for future high-frequency field-free spintronic applications [1-4]. Self-localized spin structures can substantially enrich this scope and endow new functionalities to AFM-based devices [5]. A domain wall (DW) is a topological soliton that bridges a connection between two ground states, similar to a link in a Josephson junction (JJ) between two superconductors.

We demonstrate that a DW in a bi-axial AFM with the easy-axis type of primary anisotropy and driven by a spin current is a close analogue of a long Josephson junction and the Bloch line is a close analogue to the fluxon state. Thus, the dynamics of the Néel vector inside the DW (Josephson phase Φ) is described by a sine-Gordon type of equation, where applied spin-transfer torque represents a bias current through the junction, anisotropy in a basal plane defines a plasma frequency, and characteristic speed of magnons, defined by nonhomogeneous exchange energy, corresponds to the Swihart velocity.

References:

[1] T. Jungwirth et al. Nat. Nanotech 11, 231 (2016)

[2] R. Khymyn et al., Sci. Rep. 7, 43705 (2017)

[3] O. Sulymenko et al., Phys. Rev. Appl. 8, 064007 (2017)

[4] V. Puliafito et al., Physical Review B 99, 024405 (2019)

[5] O. Gomonay et al., Nat. Phys. 14, 213 (2018)