6.5 Current-Driven Domain Wall Motion
159
Fig. 6.13 Schematic illustration of current-driven domain wall motion
6.5.1 What Will Happen if Electric Current Flow Through
This Domain Wall?
Assume that a conduction electron passes through the domain wall from left- to
right-hand side. During this passage of conduction electrons through the domain
wall, s–d interaction between the spin magnetic moment of conduction electrons
and magnetic moments at the domain wall is expected to take place. Consequently,
the spin magnetic moments of conduction electrons tend to follow the orientation
of local magnetic moments at domain wall, as demonstrated in Fig. 6.13ii. Correspondingly, the local magnetic moments at the domain wall rotate in opposite direction (Fig. 6.13iii). Thus, it comes out that a flow of electric current through the
domain wall can cause its displacement and thereby yields domain wall motion. As
already mentioned, direct observation of such current-driven domain wall motion
was possible utilizing magnetic force microscopy technique (Yamaguchi et al. 2004).
Furthermore, propagation of the domain wall has been found to be in opposite
direction to that of current direction. Moreover, the propagation direction can be
reversed by switching the polarity of this current. It is quite intriguing to point out
that this observation of current-driven domain wall motion is consistence with the
spin transfer torque mechanism.
159
Fig. 6.13 Schematic illustration of current-driven domain wall motion
6.5.1 What Will Happen if Electric Current Flow Through
This Domain Wall?
Assume that a conduction electron passes through the domain wall from left- to
right-hand side. During this passage of conduction electrons through the domain
wall, s–d interaction between the spin magnetic moment of conduction electrons
and magnetic moments at the domain wall is expected to take place. Consequently,
the spin magnetic moments of conduction electrons tend to follow the orientation
of local magnetic moments at domain wall, as demonstrated in Fig. 6.13ii. Correspondingly, the local magnetic moments at the domain wall rotate in opposite direction (Fig. 6.13iii). Thus, it comes out that a flow of electric current through the
domain wall can cause its displacement and thereby yields domain wall motion. As
already mentioned, direct observation of such current-driven domain wall motion
was possible utilizing magnetic force microscopy technique (Yamaguchi et al. 2004).
Furthermore, propagation of the domain wall has been found to be in opposite
direction to that of current direction. Moreover, the propagation direction can be
reversed by switching the polarity of this current. It is quite intriguing to point out
that this observation of current-driven domain wall motion is consistence with the
spin transfer torque mechanism.