Controlled magnetic behaviour of Ni80Fe20 nanowire by a selection of nucleation pads

Abstract

Magnetic nanowires are of technological importance as their magnetic properties can be controlled by their dimensions and shape. In soft magnetic nanowires (e.g. Ni 80 Fe 20 alloy or Permalloy), shape anisotropy has a very strong effect on their magnetic properties and thus the wire width and thickness control the domain patterns, nature of magnetization reversal, and the switching field. The switching field of a permalloy (Py) nanowire (NW) can be reduced substantially by attaching a microsized nucleation pad (NPD) to it. In this work, the OOMMF software package was used to perform micromagnetic simulations for selected NPD-NW structures. In this present study, we proved that the shape of the attached NPD is an important factor to consider. For instance, the switching field of structure comprises a triangular NPD (area = 0.25 μm2) with its head connected to a Py NW (20 nm wide) is about one fourth of the switching field of a square-like NPD-NW structure of the same size. Also the NPD size has an effect on the quality of the obtained hysteresis loop and thus it has to be comparable to the size of the NW for the sake of having a step-free hysteresis loop. These findings suggest that the rectangular NPD with its head connected to the NW may serve better than other shapes as it provides a directed motion for the domain walls to reach the NPD/NW interface easily. Thus it gives the highest reduction in the switching field of the Py nanowire in addition to a step-free hysteresis loop when the NPD size is 0.01 μm2.