(a) Schematic
illustration of a passive DW controller. The device
is divided into two regions so that the width of the spin Hall layer
is wider in one section compared to the other, but the magnetic nanowire
is uniform in width. (b) Velocity of the DW measured at various points
along the nanowire. For q > 0 μm, at 11
V pulse
(5 ns pulse), the current density drops (105 MA cm–2 to 69 MA cm–2) due to the increased width of the
Pt layer. The drop in the current density lowers vCIDWM from ∼180 m s–1 to ∼50
m s–1. (c–h) Differential Kerr microscopy
images after (c–e) injecting five consecutive pulses and (f–h)
injecting 10 consecutive pulses (10 ns long, 10 V). The orange shades
indicate the distance of the DW shift. Note that the speed of the
DW was 88 and 36 m s–1 in section 1 (narrow region)
and section 2 (wide region), respectively.