150
6 Magnetic Domain Wall Motion
resistance, R of this system is given by
R =
x
L
R ↑↑ +
L − x
L
R ↑↓
(6.1)
where, x is the position of the domain wall, L the length of the film, R ↑↑ and R ↑↓ are the
resistances for parallel and antiparallel magnetization configurations, respectively.
From Eq. 6.1, we understand that the determination of the position of the DW
in the magnetic nanowire is feasible by ‘Simple Resistance Measurement’. In our
supposed nanowire having FM/NM/FM trilayer device structure, the bottom FM
layer is considered to be thin, whereas the top FM layer is thick. Figure 6.6a exhibits
the intriguing variation of the resistance of this trilayer nanowire system as a function
of the external magnetic field.
In this case, a small magnetic field is applied at the beginning of the measurement
to achieve magnetization alignment in one ferromagnetic film in the direction of the
applied field. Subsequently, the value of the magnetic field is increased, and the corresponding resistance has been measured accordingly. Magnetoresistance measurement evidence essentially four very sharp leaps. The first and second leaps, observed
at low applied magnetic fields, correspond to the magnetization reversal of the thin
top ferromagnetic layer, whereas third and fourth leaps, obtained at high applied
Fig. 6.6 a Schematic
variation of resistance of a
trilayer spin valve structure
with applied magnetic field.
b Magnetic domain
structures can be inferred
from the resistance
measurement. Direction of
the external magnetic field is
also shown
6 Magnetic Domain Wall Motion
resistance, R of this system is given by
R =
x
L
R ↑↑ +
L − x
L
R ↑↓
(6.1)
where, x is the position of the domain wall, L the length of the film, R ↑↑ and R ↑↓ are the
resistances for parallel and antiparallel magnetization configurations, respectively.
From Eq. 6.1, we understand that the determination of the position of the DW
in the magnetic nanowire is feasible by ‘Simple Resistance Measurement’. In our
supposed nanowire having FM/NM/FM trilayer device structure, the bottom FM
layer is considered to be thin, whereas the top FM layer is thick. Figure 6.6a exhibits
the intriguing variation of the resistance of this trilayer nanowire system as a function
of the external magnetic field.
In this case, a small magnetic field is applied at the beginning of the measurement
to achieve magnetization alignment in one ferromagnetic film in the direction of the
applied field. Subsequently, the value of the magnetic field is increased, and the corresponding resistance has been measured accordingly. Magnetoresistance measurement evidence essentially four very sharp leaps. The first and second leaps, observed
at low applied magnetic fields, correspond to the magnetization reversal of the thin
top ferromagnetic layer, whereas third and fourth leaps, obtained at high applied
Fig. 6.6 a Schematic
variation of resistance of a
trilayer spin valve structure
with applied magnetic field.
b Magnetic domain
structures can be inferred
from the resistance
measurement. Direction of
the external magnetic field is
also shown