Domain Wall Programmable Magnetic Logic
241
Fig. 15 Schematic image of
the dual branch structure
with metallic strip at the
bifurcation to generate
Oersted magnetic field
the wall (inset). Moreover, the TDW assumes a characteristic triangular shape which
gives rise to a transversely varying magnetic charge concentration. The base of the
triangular spin structure always has higher charge component as compared to the
apex of the TDW.
To explore the charge distribution of the TDW for selective motion into the branch
structure, we have patterned a metallic strip at the upper edge of the nanowire to
generate Oersted field as shown in the schematic Fig. 15. When the current is applied
through the metallic strip,
Oersted field is generated that can be used to repel or attract the TDW at the
bifurcation. The TDW motion into the U-shaped half ring can be controlled depending
on the polarity of the current and the charge distribution of TDW. The Oersted field
distribution around the magnetic gate is estimated by COMSOL simulation.
Shown in Fig. 16(a) is simulated model in which the magnetic gate is overlapped
only 25% of the nanowire width. The transverse magnetic field distribution in the
NiFe nanowire due to the current is shown in Fig. 16c. It shows that the top edge
of the NiFe which is directly beneath the Au pad experiences a higher magnetic
field compared to the bottom edge of the NiFe which is away from the Au pad. The
strength of magnetic field generated by current is plotted as a function of position
along the NiFe, Fig. 16c. The field strength is estimated to be ~110 Gauss beneath
the Au pad while it is ~10 Gauss at the bottom edge when the current density is 1 ×
10
11 A/m
2 . The local Oersted field interacts with the magnetic charge of the TDW
and influences the motion of TDW having higher charge concentration along the
upper edge. This dual control of selective motion of the TDW allows the device to
perform programmable logic operation within a single structure. By simply changing
the direction of the local Oersted field, two universal logic gate operations can be
obtained.
241
Fig. 15 Schematic image of
the dual branch structure
with metallic strip at the
bifurcation to generate
Oersted magnetic field
the wall (inset). Moreover, the TDW assumes a characteristic triangular shape which
gives rise to a transversely varying magnetic charge concentration. The base of the
triangular spin structure always has higher charge component as compared to the
apex of the TDW.
To explore the charge distribution of the TDW for selective motion into the branch
structure, we have patterned a metallic strip at the upper edge of the nanowire to
generate Oersted field as shown in the schematic Fig. 15. When the current is applied
through the metallic strip,
Oersted field is generated that can be used to repel or attract the TDW at the
bifurcation. The TDW motion into the U-shaped half ring can be controlled depending
on the polarity of the current and the charge distribution of TDW. The Oersted field
distribution around the magnetic gate is estimated by COMSOL simulation.
Shown in Fig. 16(a) is simulated model in which the magnetic gate is overlapped
only 25% of the nanowire width. The transverse magnetic field distribution in the
NiFe nanowire due to the current is shown in Fig. 16c. It shows that the top edge
of the NiFe which is directly beneath the Au pad experiences a higher magnetic
field compared to the bottom edge of the NiFe which is away from the Au pad. The
strength of magnetic field generated by current is plotted as a function of position
along the NiFe, Fig. 16c. The field strength is estimated to be ~110 Gauss beneath
the Au pad while it is ~10 Gauss at the bottom edge when the current density is 1 ×
10
11 A/m
2 . The local Oersted field interacts with the magnetic charge of the TDW
and influences the motion of TDW having higher charge concentration along the
upper edge. This dual control of selective motion of the TDW allows the device to
perform programmable logic operation within a single structure. By simply changing
the direction of the local Oersted field, two universal logic gate operations can be
obtained.