252
S. Goolaup et al.
pinned at the upper edge of the structure. This results in the spins within the structure
to adopt a transverse alignment along the +y direction. When the +½ edge defect
reaches the end of the angled rectangle, a DW with same input spin configuration
exits into the conduit. Hence, the rectifier, performs a topological rectification with
the output always being −½ ~ +½. As topological edge defects are consistent for
Head-to-Head and Tail-to-Tail DW, irrespective of the transverse component of the
wall, the structure allows for the topological rectification of the TDW. By mirroring
the angled rectangle along the nanowire length, such that the spins within the angled
rectangle influences the lower edge of the nanowire, the structure can perform a
topological rectification with the output always being +½ ~ −½.
Experimental Verification of Rectifier
Experimental verification of the rectifier is conducted by exploiting the chirality
dependent selective movement of TDW in a branch structure. For a +½ ~ −½ TDW
flowing through a branch structure, the conservation of the topological defect results
in the TDW moving along the upper edge of a Y shape structure. Conversely, for a
−½ ~ +½ winding number, the TDW will move to the lower branch of the Y shape
structure.
We have experimentally verified this principle using the same nanowire conduit
dimensions as the rectifier structure. The topological detector is shown in the scanning
electron microscope image. A nucleation pad with a transverse nanowire, acting as
a selector is used, so as to ensure proper control on the type of TDW being injected
in the conduit. The selector sets the transverse component of the DW exiting the
nucleation pad. The Y-shape detector comprises of two wire angled at ~ 70° from
the horizontal. To ensure that the TDW is the stable configuration, the width of the
nanowire conduit, DW detector and selector are kept at 120 nm.
To test the rectifier structure, the angled rectangle is patterned along the nanowire
conduit, as seen in Fig. 23a. The rectifier has a width of ~240 nm (~2 × w) and length
~480 nm (~4 × w), angled with respect to the horizontal axis, at ~ +11°, for rectifier
(Fig. 23a). The selector is initially set along the +y direction, characterized by bright
and dark contrasts, and the spins along the conduit are aligned the +x direction as
seen in Fig 23(b)I. By increasing the external field to 150 Oe, along the −x direction,
a TTU DW (−½ ~ +½ winding numbers) is injected into the conduit, as seen in
the MFM image, Fig. 23b-II. The lower branch of the detector changes direction, as
evident from the MFM image of Fig. 23b-II. This implies that the DW exiting the
rectifier has as −½ ~ +½ winding numbers, implying that the TTU DW does not
undergo any topological change as it moves through the rectifier.
The MFM configuration when the selector and conduit are magnetized along the
−y and +x direction respectively, is shown in Fig. 23c-I. As expected, the selector
has a bright and dark contrast on the upper and lower edges. Following the application
of a field of 150 Oe along the −x direction, the contrast of the lower branch of the
detector changes to bright, as can be seen in Fig. 23c-II. This indicates that a DW
with winding numbers of −½ ~ +½, reached the detector. As the nucleated DW
has a topological edge defect of +½ ~ −½, this implies that structure A effectively,
rectifies the output of any incoming DW to a −½ ~ +½ configuration.
S. Goolaup et al.
pinned at the upper edge of the structure. This results in the spins within the structure
to adopt a transverse alignment along the +y direction. When the +½ edge defect
reaches the end of the angled rectangle, a DW with same input spin configuration
exits into the conduit. Hence, the rectifier, performs a topological rectification with
the output always being −½ ~ +½. As topological edge defects are consistent for
Head-to-Head and Tail-to-Tail DW, irrespective of the transverse component of the
wall, the structure allows for the topological rectification of the TDW. By mirroring
the angled rectangle along the nanowire length, such that the spins within the angled
rectangle influences the lower edge of the nanowire, the structure can perform a
topological rectification with the output always being +½ ~ −½.
Experimental Verification of Rectifier
Experimental verification of the rectifier is conducted by exploiting the chirality
dependent selective movement of TDW in a branch structure. For a +½ ~ −½ TDW
flowing through a branch structure, the conservation of the topological defect results
in the TDW moving along the upper edge of a Y shape structure. Conversely, for a
−½ ~ +½ winding number, the TDW will move to the lower branch of the Y shape
structure.
We have experimentally verified this principle using the same nanowire conduit
dimensions as the rectifier structure. The topological detector is shown in the scanning
electron microscope image. A nucleation pad with a transverse nanowire, acting as
a selector is used, so as to ensure proper control on the type of TDW being injected
in the conduit. The selector sets the transverse component of the DW exiting the
nucleation pad. The Y-shape detector comprises of two wire angled at ~ 70° from
the horizontal. To ensure that the TDW is the stable configuration, the width of the
nanowire conduit, DW detector and selector are kept at 120 nm.
To test the rectifier structure, the angled rectangle is patterned along the nanowire
conduit, as seen in Fig. 23a. The rectifier has a width of ~240 nm (~2 × w) and length
~480 nm (~4 × w), angled with respect to the horizontal axis, at ~ +11°, for rectifier
(Fig. 23a). The selector is initially set along the +y direction, characterized by bright
and dark contrasts, and the spins along the conduit are aligned the +x direction as
seen in Fig 23(b)I. By increasing the external field to 150 Oe, along the −x direction,
a TTU DW (−½ ~ +½ winding numbers) is injected into the conduit, as seen in
the MFM image, Fig. 23b-II. The lower branch of the detector changes direction, as
evident from the MFM image of Fig. 23b-II. This implies that the DW exiting the
rectifier has as −½ ~ +½ winding numbers, implying that the TTU DW does not
undergo any topological change as it moves through the rectifier.
The MFM configuration when the selector and conduit are magnetized along the
−y and +x direction respectively, is shown in Fig. 23c-I. As expected, the selector
has a bright and dark contrast on the upper and lower edges. Following the application
of a field of 150 Oe along the −x direction, the contrast of the lower branch of the
detector changes to bright, as can be seen in Fig. 23c-II. This indicates that a DW
with winding numbers of −½ ~ +½, reached the detector. As the nucleated DW
has a topological edge defect of +½ ~ −½, this implies that structure A effectively,
rectifies the output of any incoming DW to a −½ ~ +½ configuration.