Sequential snap shots
of current-induced DW motion in multisectioned
device. (a)–(e) Forward propagation of two DWs. Series of 22
V, 5 ns long pulses are injected to position the DWs in each section
(section 1, left-narrow to section 5, right-wide). The DW spacing
in each section were 8.1, 6.4, 4.2, 2.1, and 1 μm, respectively.
(f)–(j) Backward propagation of two DWs. The shift-back process
was achieved by 5 ns long pulses with an amplitude of negative 22
V. The DW spacing was decompressed from 1 μm ± 0.5 to 8.6
μm ± 0.5 μm upon the return of the DWs to the original
position. The DW spacings in each section were 1, 1.4, 3.3, 6.9, and
8.6 μm, respectively. (k) Summary of the DW spacing and compression
rate changes in different sections (green: motion from left (high J) to right (low J); orange: motion from
right (low J) to left (high J)).