Magnetic domain evolution in permalloy mesoscopic dots

Abstract

Permalloy (Ni80Fe20) squares (30 nm thick and w mu m wide; 1 less than or equal to w less than or equal to 200 mu m) and circular disks (30 nm thick and r mu m diameter; 1 less than or equal to r less than or equal to 200 mu m) prepared on a GaAs (100) substrate were observed in both their demagnetized and remanent states by magnetic force microscopy (MFM) associated with non-contact atomic force microscopy (NC-AFM). The squares (2 less than or equal to w mu m) exhibited conventional closure domains and the corner plays a very important role in creating new walls. The circular disks, on the other hand, formed either vortex domain (5 less than or equal to r less than or equal to 20 mu m) or multi-domain (50 less than or equal to r mu m) states, The magnetization rotation is observed by MFM to change according to the size and shape of the elements, The MFM observations are supported by micromagnetic calculations which confirm the effect of the corner on the domain wall formation

Magnetic domain studies of permalloy wire-based structures with junctions

“…The ring chain also shows flux closure domains as observed in the circular dots [9] and single rings [see Fig. 3(c)].…”

“…A commercial Si probe coated with CoCr (Digital Instruments, Pointprobe magnetic force sensor MESP) was used and the distance between probe and sample was set as 5 nm for tapping mode AFM and 100 nm for MFM measurements [9], [10]. The tip of the probe was magnetized before each observation.…”

“…The system was divided into 30 nm cubic cells, since we obtain reasonable domain configurations with this mesh size [2], [4], [9]. The demagnetization field, magnetic anisotropy field and the exchange field were calculated at the position of each cell.…”

“…Micromagnetic numerical calculations were carried out to confirm the energetically stable magnetic domain configurations using a finite difference method [9]. The system was divided into 30 nm cubic cells, since we obtain reasonable domain configurations with this mesh size [2], [4], [9].…”

Effect of rounded corners on the magnetic properties of pyramidal-shaped shell structures

“…However, realistic structures contain non-ideal features like surface roughness and a rounding of corners and edges. The important effect of a rounding of corners and edges on the formation of magnetic states has already been demonstrated before [2,3].…”