Abstract
Spintronic devices currently rely on magnetic switching or controlled motion of domain walls (DWs) by an external magnetic field or a spin-polarized current. Controlling the position of DW is essential for defining the state/information in a magnetic memory. During the process of nanowire fabrication, creating an off-set of two parts of the device could help to pin DW at a precise position. Micromagnetic simulation conducted on in-plane magnetic anisotropy materials shows the effectiveness of the proposed design for pinning DW at the nanoconstriction region. The critical current for moving DW from one state to the other is strongly dependent on nanoconstricted region (width and length) and the magnetic properties of the material. The DW speed which is essential for fast writing of the data could reach values in the range of hundreds m/s. Furthermore, evidence of multi-bit per cell memory is demonstrated via a magnetic nanowire with more than one constriction.
Highlights
The magnetic material properties such as anisotropy energy Ku and saturation magnetization Ms Figure 1(b) shows the case of multi-step device for multi-bit per cell magnetic memory device
In the first part of this study, the effect of stepped region dimension l and d on domain wall (DW) dynamics is investigated while in a second part, we were interested in the correlation between the magnetic properties and DW stability
We have demonstrated that in magnetic nanowire with a stepped region, DW could be precisely pinned
Summary
We consider a magnetic nanowire of length L, width W, and thickness t with a stepped region. This means that stabilizing DW within the vicinity of stepped region is possible by selecting the optimal values of d and l for each applied current density. Similar to the study conducted on Ku effect on DW dynamics shown above (Figs 4 and 5), it was observed that there is a minimum Ms value for stabilizing DW at the stepped region. The bold arrows show the critical Ms separating non-pinned and pinned DW ranges This critical value depends on the current density, device dimension and Ku. It is important to mention about the relatively large values of DW velocity obtained from the time dependence of mx which is beneficial for a fast writing of data by a polarized electric current.
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