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Proposed structures enabling electrostatic control of DW transfer in a FMI. (a) Device design employing two nanowire gates to modulate the carrier profile in the graphene (MG) layer and, thus, the effective magnetic field in the FMI via the exchange interaction. The DW is confined in the middle region by two FMMs with opposite magnetization. (b) Cascade structure extending the range of DW motion. The DW can move past each gate by sequential application of bias pulses.
Sample calculation of DW dynamics when the effective magnetic field in the FMI is obtained via a linear doping gradient in graphene from n– to p–type. In reference to the curve in the middle, those on the right and the left describe the cases when μ is raised or lowered by 0.1 eV, respectively. The arrows represent one possible transition loop when bias pulses are applied to shift μ electrically. Two horizontal dotted lines denote the uniform pinning field of 30 Oe.
Effective magnetic field H eff as a function of DW position in the FMI layer of the structure shown in Fig. 1(a). Two different materials are considered for the gate dielectric; TiO 2 and HfO 2 . In the case of TiO 2 , the dielectric thickness is varied (A—30 nm; B—40 nm; and C—50 nm), while the gate voltages are fixed at ±1 V. For HfO 2 (D), a thickness of 30 nm is used along with the gate voltages of ± 2.5 V. In all cases, the equilibrium electron density of μ − εD = 0.3 eV is assumed for graphene. The inset shows temporal evolution of the DW position in the TiO 2 cases as Vg 1 = +1 V and Vg 2 = −1 V are applied at t = 0.
Calculated magnetization switching dynamics for 1.5 cycles. The dashed line shows the corresponding pulse sequence. The case with 40-nm TiO2 is considered with the gate bias pulses of ±1 V or V.
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