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S. Goolaup et al.
from the inverter switched the upper branch of the detector. This implies that the
HHD (−½ ~ +½) TWD has been transformed into an HHU (+½ ~ −½) TWD.
The above results show that it is possible to control the winding numbers of TDW
in magnetic nanowires by exploiting the relaxation process of a DW passing through
an angled rectangle. This work paves the way for technique employing DW profile
(winding numbers) for performing logical operation. The TDW can be considered as
a mobile data bit and the information is encoded as the transverse profile of the DW.
This concept can be exported to chiral DW in materials with perpendicular magnetic
anisotropy.
Even though the fabricated structures have slight variations, as seen from the SEM
image of Figs. 23 and 25, the topological rectification/inversion is still possible as
evidence from the MFM measurements. The variation in the shape of the structure
does not affect the rectification/inversion process, as the device exploits the inherent
internal DW profile for pinning/depinning at the modulation. This shows that this
technique is robust and can be applied experimentally for various technological
applications.
The field needed for the rectification/inversion operation is lower in experiment
as compared to micromagnetic simulation is attributed to thermally activated depinning [42]. A field of 150 Oe, for device operation, may inevitably lead to Walker
breakdown, which will affect the integrity of the DW. The fidelity length of a TDW
decreases asymptotically to around 350 nm at high fields [33]. Additionally, it has
been reported that edge defects along the nanowire conduit may also lead to shift
Walker breakdown to higher field [43]. For all our samples, the nanowire conduit
length between the nucleation pad to the rectifier/inverter and subsequently the
detector, is kept to 200 nm. This is well below the reported fidelity length of TDW and
ensures that the integrity of our input and output DW are not compromised. However,
for practical applications, the nanowire conduit may be structurally modulated hereby
stabilising DW and preserving its chirality over large distances [44].
4 Summary
In this chapter, we have demonstrated the concept of manipulating information
by engineering the internal structure of transverse domain wall. By exploiting the
dynamics on domain wall within defined structures, different types of logical operations can be carried out. We show that by leveraging on the charge intrinsic to the
transverse domain wall profile, a gate programmable reconfigurable logic structure
can be designed. The structure is capable of carrying out all the logical operations and
more importantly produce complementary output. Finally, we show that by modulation the propagation of the domain wall through modulated nanowires, the profile
of the transverse domain wall can be deterministically controlled, enabling a novel
paradigm in magnetic logic. The domain wall profile for logic operation can be further
extended to domain walls in materials with perpendicular magnetic anisotropy.
S. Goolaup et al.
from the inverter switched the upper branch of the detector. This implies that the
HHD (−½ ~ +½) TWD has been transformed into an HHU (+½ ~ −½) TWD.
The above results show that it is possible to control the winding numbers of TDW
in magnetic nanowires by exploiting the relaxation process of a DW passing through
an angled rectangle. This work paves the way for technique employing DW profile
(winding numbers) for performing logical operation. The TDW can be considered as
a mobile data bit and the information is encoded as the transverse profile of the DW.
This concept can be exported to chiral DW in materials with perpendicular magnetic
anisotropy.
Even though the fabricated structures have slight variations, as seen from the SEM
image of Figs. 23 and 25, the topological rectification/inversion is still possible as
evidence from the MFM measurements. The variation in the shape of the structure
does not affect the rectification/inversion process, as the device exploits the inherent
internal DW profile for pinning/depinning at the modulation. This shows that this
technique is robust and can be applied experimentally for various technological
applications.
The field needed for the rectification/inversion operation is lower in experiment
as compared to micromagnetic simulation is attributed to thermally activated depinning [42]. A field of 150 Oe, for device operation, may inevitably lead to Walker
breakdown, which will affect the integrity of the DW. The fidelity length of a TDW
decreases asymptotically to around 350 nm at high fields [33]. Additionally, it has
been reported that edge defects along the nanowire conduit may also lead to shift
Walker breakdown to higher field [43]. For all our samples, the nanowire conduit
length between the nucleation pad to the rectifier/inverter and subsequently the
detector, is kept to 200 nm. This is well below the reported fidelity length of TDW and
ensures that the integrity of our input and output DW are not compromised. However,
for practical applications, the nanowire conduit may be structurally modulated hereby
stabilising DW and preserving its chirality over large distances [44].
4 Summary
In this chapter, we have demonstrated the concept of manipulating information
by engineering the internal structure of transverse domain wall. By exploiting the
dynamics on domain wall within defined structures, different types of logical operations can be carried out. We show that by leveraging on the charge intrinsic to the
transverse domain wall profile, a gate programmable reconfigurable logic structure
can be designed. The structure is capable of carrying out all the logical operations and
more importantly produce complementary output. Finally, we show that by modulation the propagation of the domain wall through modulated nanowires, the profile
of the transverse domain wall can be deterministically controlled, enabling a novel
paradigm in magnetic logic. The domain wall profile for logic operation can be further
extended to domain walls in materials with perpendicular magnetic anisotropy.