Observation of Magnetization Reversal Process in Ni–Fe Nanowire Using Magnetic Field Sweeping-Magnetic Force Microscopy

Abstract

The details of the magnetization reversal process of Ni–Fe nanowires, which were 10, 30, and 50-nm thick, were successfully observed using our newly proposed magnetization measurement method, namely, magnetic field sweeping (MFS)-magnetic force microscopy (MFM). All the points within the nanowire show marked phase changes (stray fields change) as the magnetic field is varied. In particular, each nanowire edge displays a hysteresis loop, while the center shows a sharp jump or a plateau area. These results demonstrate that domain wall motion is dominant in the magnetization reversal process of a 10-nm-thick Ni–Fe nanowire and that domain wall motion along with domain wall pinning play important roles in the magnetization reversal process in both 30- and 50-nm-thick Ni–Fe nanowires.

Local Probing of Vortex Core Movement in a Ni–Fe Disk Using Magnetic Field Sweeping-Magnetic Force Microscopy

“…This frequency shift corresponds to the change in phase within a disk measured by MFS-MFM, because the MFM tip used in this method was initially magnetized in the perpendicular direction and the perpendicular component of the stray field was detected. [12][13][14][15] Accordingly, changes in the z-derivative of the stray field (À1=M s Á dH z =dz) at points A and B with magnetic field were also computed using the MFM contrasts at various magnetic fields of a Ni-Fe disk obtained from the micromagnetics simulation. 16) These results are shown in Fig.…”

“…Hence, we have proposed a new magnetization measurement method, magnetic field sweeping (MFS)-MFM, [12][13][14][15] which uses a MFM tip as a detector while the magnetic field is swept. MFS-MFM has advantages in that it enables the direct observation of the precise magnetic state at a local point within a single nanosized magnet at room temperature, the shape of the specimens is not restricted, and the measuring time is less than 1 min.…”

“…We have successfully observed the details of the domain wall motion and the magnetization reversal at local points within an isolated nanowire and a dot using MFS-MFM. [12][13][14][15] In this study, we examined the local probing of the vortex core movement in a Ni-Fe disk with the vortex state using MFS-MFM. We also investigated the chirality of the vortex core in the disk using MFS-MFM.…”