Injection of a magnetic domain wall into a submicron magnetic wire

Two types of magnetic wires (150 nm width) with trilayer structure consisting of NiFe (20 nm)/Cu (20 nm)/Co (20 nm) were prepared. One was connected to a square pad $\text{(0.5×0.5\hspace{0.05em}μ}{\mathrm{m}}^{\mathrm{2}})$ at one end, while the other has a symmetrical shape with two flat ends. Magnetization reversal was detected sensitively by magnetoresistance measurement. Switching field of the Co layer for the wire with a pad was much smaller than that for the wire without a pad. This indicates that a domain wall nucleates initially in the pad and is injected into the wire at the switching field. This model for the magnetization reversal process is supported by the angular dependence of the switching field.