Coherent spin waves driving domain wall motion in insulators – Nature Nanotechnology

Magnetic domain walls can modulate spin-wave transport in perpendicularly magnetized channels, while magnon spin current can drive domain wall motion in the bi-doped yttrium iron garnet channel device.

Since the proposal of the magnetic racetrack concept, the motion of magnetic domains and domain walls (DW) with spin currents has been an important area of research in spintronics as it enables the development of true 3D magnetic data storage¹. In parallel, the field of magnonics has emerged to exploit the elementary collective excitations of the magnetic system, spin waves (SW), and their quanta, magnons, to construct low-power nanoscale data processing devices based on coherent waves². Now, writing in Nature Nanotechnology, Fan et al. have made a breakthrough that brings the two fields together by moving magnetic domain walls in an insulator using coherently excited spin waves as spin current carriers³. For the efficient application of this magnonic spin torque, the use of a special magnetic insulator, namely bi-doped yttrium iron garnet (Bi-YIG), with its very low attenuation for magnons, is crucial. Due to the low power dissipation, the energies required to move the domain walls are orders of magnitude lower than in previous experiments with metallic films. Due to the long decay length of the magnons and the low DW pinning, the DWs can even be moved by short, nanosecond magnon pulses over tens of micrometres. This opens the way to charge-current-free magnetic logic combining spin waves as data carriers and magnetic domain walls as memory bits.