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6 Magnetic Domain Wall Motion
6.3.3 Rachet Effect in Spintronics
Structure
In order to discuss rachet effect in spintronics, let us consider a trilayer magnetic
nanowire, consisting of Ni 81 Fe 19 (5 nm)/Cu (20 nm)/Ni 81 Fe 19 (20 nm). Figure 6.8
illustrates the schematic representation of the top view of the nanowire (Himeno et al.
2005b). The completed structure is fabricated onto thermally oxidized Si substrates
by e-beam lithography and lift-off method. The uniqueness of this nanowire structure is that its main body consists of four asymmetric shaped notches. In order to
measure current and voltages, four probes have been constructed by a non-magnetic
material (Cu). Furthermore, two narrow Cu wires are attached crossing the ends
of the magnetic wire and there is a wide Cu wire protecting the notched part of
the magnetic nanowire. Finally, these Cu wires are electrically insulated from the
magnetic nanowire by SiO 2 layers.
Fig. 6.8 Schematic representation of top view of a trilayer special kind of magnetic wire having
NiFe (5 nm)/Cu (20 nm)/NiFe (20 nm) spin valve structure for demonstrating ratchet effect