Visualization of the Barkhausen effect by magnetic force microscopy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Granular ferromagnetic thin films with perpendicular anisotropy are crucial for magnetic storage technologies.
• Understanding magnetization reversal at the nanoscale is key to improving device performance and data integrity.
• The Barkhausen effect provides insights into the discrete nature of magnetic domain changes.

Purpose of the Study:

• To investigate the physical principles governing magnetization reversal in granular ferromagnetic thin films.
• To differentiate and characterize individual Barkhausen volumes during magnetization reversal.
• To analyze the statistical distributions of Barkhausen volumes to understand nucleation and domain wall propagation mechanisms.

Main Methods:

• Utilizing magnetic force microscopy (MFM) to visualize the Barkhausen effect.
• Localizing and distinguishing individual Barkhausen volumes based on their formation process (nucleation vs. domain wall growth).
• Analyzing the size distributions of these Barkhausen volumes.

Main Results:

• Successfully visualized and differentiated between newly nucleated and domain wall-grown Barkhausen volumes.
• Observed a Gaussian size distribution for nucleated Barkhausen volumes, suggesting random nucleation.
• Found an inverse power law distribution for grown Barkhausen volumes, indicating critical behavior during domain wall motion.

Conclusions:

• The study provides detailed insights into the physical principles of magnetization reversal in granular ferromagnetic thin films.
• Nucleation and domain wall propagation are distinct processes with different statistical characteristics.
• The observed inverse power law distribution suggests scale-invariant behavior during domain wall propagation, hinting at critical phenomena.