Domain Wall Programmable Magnetic Logic
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x direction. Hence the output state at the LHR is logical bit “1”, while that for the
UHR is logical bit “0”.
Inputs “0” and “1”: In this particular logic combination, the magnetisation orientation of the horizontal nanowire (Input 2) is aligned along the +x direction. This
configuration for Input 2 presets the outputs of the device (UHR and LHR) to logical
“1”. Following the application of a linear magnetic field of 100 Oe along the −x
direction, a TT TDW propagates through the horizontal nanowire (Input 2). MFM
imaging after the field application reveals a change in the magnetic contrast at the
UHR from dark to bright, as seen in Fig. 18-ii. The transverse component of the
injected TT-DW points to the −y direction (“DOWN” chirality) as dictated by the
vertical nanowire (Input 1) magnetic configuration. For a TT-D TDW, the higher
charge concentration is at the upper edge of the horizontal nanowire. In this case,
the attraction from the Oersted field overcomes the potential barrier created by the
asymmetry at the bifurcation.
The Oersted field from the magnetic gate attracts and guides the TT-D TDW
into the UHR. Consequently, the UHR magnetisation orientation is switched, representing a change from logical bit “1” to “0”. The magnetisation of the LHR remains
unchanged, i.e. at logical bit “1”. Without the Oersted field from the magnetic gate,
the TT-D TDW would move into the LHR as dictated by the asymmetry of the structure. For our design, the minimum current density required to generate the Oersted
field to overcome the potential barrier created along the UHR was ~5 × 10
11 A/m
2 .
Inputs “1” and “0”: In this configuration, the magnetisation orientation of Input 1
is aligned along +y direction (“1”) and the magnetisation orientation of Input 2 is
aligned along the −x direction (“0”). The MFM image of the final state, following
the application of 100 Oe driving magnetic field along +x direction. The magnetic
contrast change at the LHR indicates the switching of magnetisation orientation of
the LHR. A HH-U TDW is injected at the bifurcation as the magnetisation orientation
in Input 1 is aligned along +y direction. Similar to the case of “0” and “0”, the HH-U
TDW is influenced by both the local Oersted field and asymmetry. As such, the HH-U
TDW moves into the LHR resulting in the reversal of the magnetisation orientation
to +x direction, which corresponds to an output bit of “1”. The logical state of the
UHR remains unchanged as logical bit “0”.
Inputs “1” and “1”: When the magnetisation orientations of the vertical and horizontal nanowires are aligned along the +y and +x directions, respectively, both
logical input bits (Input 1 and Input 2) are “1”. Under the external magnetic field,
a TT-U TDW is injected into the structure. For this TDW configuration, the higher
charge concentration is along the lower edge of the nanowire. MFM image of the
structure after 100 Oe field application along −x direction shows that the magnetisation orientation of LHR has switched as seen in Fig. 18-IV. The effect of the Oersted
field from the magnetic gate on the TT-U TDW is negligible as the higher charge
concentration of the DW is at the lower edge of the nanowire. The effect of asymmetry overpowers the attraction from local Oersted field at the bifurcation. This leads
to the TT-U TDW motion into the LHR which switches the magnetisation orientation
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x direction. Hence the output state at the LHR is logical bit “1”, while that for the
UHR is logical bit “0”.
Inputs “0” and “1”: In this particular logic combination, the magnetisation orientation of the horizontal nanowire (Input 2) is aligned along the +x direction. This
configuration for Input 2 presets the outputs of the device (UHR and LHR) to logical
“1”. Following the application of a linear magnetic field of 100 Oe along the −x
direction, a TT TDW propagates through the horizontal nanowire (Input 2). MFM
imaging after the field application reveals a change in the magnetic contrast at the
UHR from dark to bright, as seen in Fig. 18-ii. The transverse component of the
injected TT-DW points to the −y direction (“DOWN” chirality) as dictated by the
vertical nanowire (Input 1) magnetic configuration. For a TT-D TDW, the higher
charge concentration is at the upper edge of the horizontal nanowire. In this case,
the attraction from the Oersted field overcomes the potential barrier created by the
asymmetry at the bifurcation.
The Oersted field from the magnetic gate attracts and guides the TT-D TDW
into the UHR. Consequently, the UHR magnetisation orientation is switched, representing a change from logical bit “1” to “0”. The magnetisation of the LHR remains
unchanged, i.e. at logical bit “1”. Without the Oersted field from the magnetic gate,
the TT-D TDW would move into the LHR as dictated by the asymmetry of the structure. For our design, the minimum current density required to generate the Oersted
field to overcome the potential barrier created along the UHR was ~5 × 10
11 A/m
2 .
Inputs “1” and “0”: In this configuration, the magnetisation orientation of Input 1
is aligned along +y direction (“1”) and the magnetisation orientation of Input 2 is
aligned along the −x direction (“0”). The MFM image of the final state, following
the application of 100 Oe driving magnetic field along +x direction. The magnetic
contrast change at the LHR indicates the switching of magnetisation orientation of
the LHR. A HH-U TDW is injected at the bifurcation as the magnetisation orientation
in Input 1 is aligned along +y direction. Similar to the case of “0” and “0”, the HH-U
TDW is influenced by both the local Oersted field and asymmetry. As such, the HH-U
TDW moves into the LHR resulting in the reversal of the magnetisation orientation
to +x direction, which corresponds to an output bit of “1”. The logical state of the
UHR remains unchanged as logical bit “0”.
Inputs “1” and “1”: When the magnetisation orientations of the vertical and horizontal nanowires are aligned along the +y and +x directions, respectively, both
logical input bits (Input 1 and Input 2) are “1”. Under the external magnetic field,
a TT-U TDW is injected into the structure. For this TDW configuration, the higher
charge concentration is along the lower edge of the nanowire. MFM image of the
structure after 100 Oe field application along −x direction shows that the magnetisation orientation of LHR has switched as seen in Fig. 18-IV. The effect of the Oersted
field from the magnetic gate on the TT-U TDW is negligible as the higher charge
concentration of the DW is at the lower edge of the nanowire. The effect of asymmetry overpowers the attraction from local Oersted field at the bifurcation. This leads
to the TT-U TDW motion into the LHR which switches the magnetisation orientation