Domain-wall memory devices, in which the information is stored in nanowires, are expected to replace hard disk drives. A problem that remains to be solved in domain-wall memory is to pin the domain walls in a controllable manner at the nanometer scale using simple fabrication. We demonstrate the possibility to stabilize domain walls by making staggered nanowires. Controllable domain-wall movement is exhibited in permalloy nanowires using magnetic fields where the pinning field is about 10 mT. The pinning field and stability of the domain walls can be increased by adjusting the offset dimensions of the staggered nanowires. Domain-wall velocities of about 200 m/s are computed for the experimentally used permalloy nanowires. Domain-wall velocities are found to be independent of pinning strength and stability, providing a way to tune the pinning without compromising domain-wall velocities.

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.

The effect of annealing on the diffusion induced changes in the magnetic and magnetodynamic properties of (Co/Ni) multilayers were investigated. Here, we report, all aspects of post annealing induced effect on perpendicular magnetic anisotropy (PMA), domain morphology, switching mechanism and high frequency magnetization dynamics to understand spin relaxation. (Co/Ni) multilayers of this study exhibited a loop squareness of 95%, a slight drop in saturation magnetization from 650 emu/cc to 620 emu/cc and high magnetic anisotropy ( K _u ~ 3 × 10 ⁵ J m ⁻³ ) even after annealing at temperatures as high as 400 °C. Successive domain mapping by magnetic force microscopy revealed characteristics of multi-domains stripe that feature at all stages of annealing except at 500 °C, attributed to the loss of PMA, driven by interfacial diffusion. High frequency broadband ferromagnetic resonance measurements showed little effect of annealing on intrinsic damping parameter ( α = 0.019–0.024) while inhomogeneous linewidth broadening varied without a clear trend. These results are discussed considering crystallographic modifications and it was found that fcc (1 1 1) texture was retained in the samples until 400 °C post annealing. The retention of a high anisotropy, high magnetization and low damping constant after high temperature annealing makes these Co/Ni multilayers suitable for designing spin torque based memory devices.