Inertia-Free Thermally Driven Domain-Wall Motion in Antiferromagnets

Domain-wall motion in antiferromagnets triggered by thermally induced magnonic spin currents is studied theoretically. It is shown by numerical calculations based on a classical spin model that the wall moves towards the hotter regions, as in ferromagnets. However, for larger driving forces the so-called Walker breakdown—which usually speeds down the wall—is missing. This is due to the fact that the wall is not tilted during its motion. For the same reason antiferromagnetic walls have no inertia and, hence, no acceleration phase leading to higher effective mobility.

Figure 1

Motion of the DW in a thermal gradient. Linear temperature gradient $\mathrm{\Delta }T/\mathrm{\Delta }z=0.56\times {10}^{-3}{T}_c/a$ (a), and profile of the DW at different times in a ferromagnetic (b), and antiferromagnetic (c) system with $d_x=0.02\mathrm{J}$.

Figure 2

Displacement of the DW versus time. Comparison between ferromagnetic (solid) and antiferromagnetic (dashed) systems with different intermediate anisotropies $d_x$ in a thermal gradient of $\mathrm{\Delta }T/\mathrm{\Delta }z=1.67\times {10}^{-3}{T}_c/a$.

Figure 3

Sketch of the torques acting on the central plane of a DW in a thermal gradient. The two sublattices of the AFM are occupied with blue and yellow spins, respectively.

Figure 4

DW velocity as a function of temperature gradient in an antiferromagnetic (red) and a ferromagnetic (blue) system with (a) $d_x=0.02\mathrm{J}$ and (b) $d_x=0.01\mathrm{J}$. Comparison between numerical results (points) and analytical estimates (lines).