Shape critical properties of patterned Permalloy thin films

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Understanding magnetization reversal in reduced-dimension magnetic elements is key for developing advanced magnetic devices.
• The influence of geometric features like shape and edges on magnetic properties is a critical area of research.

Purpose of the Study:

• To investigate the effects of shape and edges on magnetization reversal in cross- and framed cross-shaped Ni79Fe21 (30nm) films.
• To visualize and analyze domain structure formation and evolution during magnetization reversal.

Main Methods:

• Fabrication of patterned Ni79Fe21 films with varying stripe widths (3-30 microm).
• Magneto-optical indicator film (MOIF) technique for visualizing remagnetization.
• Experimental observation and simulation of magnetic domain structures.

Main Results:

• Identified three distinct types of domain structure evolution during magnetization reversal.
• Observed spin rotation with cross-tie structures in perpendicular stripes.
• Found nucleation and motion of coupled vortices along edges of parallel stripes.
• Demonstrated inverse proportionality between nucleation field and stripe width for parallel stripes.
• Highlighted the crucial role of magnetostatic fields at edges and intersections.

Conclusions:

• The shape and edges of magnetic elements significantly influence magnetization reversal mechanisms.
• Magnetostatic fields at geometric features are critical for controlling spin inhomogeneities and switching.
• Stripe width directly impacts the critical field for domain wall nucleation and motion.