Domain Wall Motion by the Magnonic Spin Seebeck Effect

The recently discovered spin Seebeck effect refers to a spin current induced by a temperature gradient in a ferromagnetic material. It combines spin degrees of freedom with caloric properties, opening the door for the invention of new, spin caloritronic devices. Using spin model simulations as well as an innovative, multiscale micromagnetic framework we show that magnonic spin currents caused by temperature gradients lead to spin transfer torque effects, which can drag a domain wall in a ferromagnetic nanostructure towards the hotter part of the wire. This effect opens new perspectives for the control and manipulation of domain structures.

Figure 1

(a) Temperature dependence of the free energy $\Delta F/J$ and the internal energy $\Delta E/J$ of a DW in a high anisotropic ferromagnet from spin model simulations [15] where $J$ is the sum over all exchange integrals for a single atomic spin. The reduced magnetization is also shown for comparison. The $T_{\mathrm{C}}$ is about 700 K. (b) Sketch illustrating the magnon current through a DW leading to DW motion when conservation of angular momentum is assumed.

Figure 2

All three magnetization components of the DW profiles at different times ($t_1=0.0\mathrm{ns}$, $t_2=0.5\mathrm{ns}$, and $t_3=1\mathrm{ns}$). $\lambda =0.1$ and $dT/dx=0.197\mathrm{K}/\mathrm{nm}$.

Figure 3

(a) DW position versus time for two different temperature gradients. (b) DW velocity versus temperature gradient for two different damping constants $\lambda$.