Manipulating the helical phase of chiral magnets with electric currents

Jan Masell, Xiuzhen Z. Yu, Naoya Kanazawa, Yoshinori Tokura, Naoto Nagaosa

Published 2020-07-07Version 1

The competition between the ferromagnetic exchange interaction and anti-symmetric Dzyaloshinskii-Moriya interaction can stabilize a helical phase or support the formation of skyrmions. While skyrmions and lattices of such are widely studied and known to be manipulable by electric currents, the structurally less complex helical phase is stronger pinned by defects. In thin films of chiral magnets, however, the current density can be large enough to unpin the helical phase and reveal its fascinating dynamics. We theoretically study the dynamics of the helical phase under spin-transfer torques that reveal distinct orientation processes, driven by topological defects in the bulk or induced by edges, and instabilities at larger currents. Our experiments confirm the possibility of on-demand switching the helix orientation by current pulses. Finally, we propose a novel design for memory devices that exploits the orientation of the helical phase as new order parameter.