Mesoscopic resistance fluctuations in cobalt nanoparticles

Area of Science:

• Condensed matter physics
• Nanotechnology
• Spintronics

Background:

• Mesoscopic resistance fluctuations provide insights into electron transport in nanostructures.
• Magnetization reversal processes in magnetic nanoparticles are crucial for data storage applications.

Purpose of the Study:

• To investigate the relationship between bias voltage-dependent resistance fluctuations (bias fingerprints) and magnetization reversal in cobalt nanoparticles.
• To understand the origin of the electron wave function-phase shift observed during domain wall motion.

Main Methods:

• Measurements of mesoscopic resistance fluctuations in cobalt nanoparticles.
• Analysis of bias fingerprints in response to magnetization-reversal processes.
• Theoretical explanation of the observed phase shift.

Main Results:

• Bias fingerprints were observed to rearrange during domain nucleation and annihilation.
• A significant electron wave function-phase shift of approximately 5π was detected, attributed to domain walls.
• The phase shift was explained by the mistracking effect, where electron spins lag behind magnetic moments within the domain wall, rather than the Aharonov-Bohm effect.
• A short dephasing time (τφ ≈ 1 ps) at 0.03 K in cobalt was observed and linked to strong magnetocrystalline anisotropy.

Conclusions:

• Magnetization reversal dynamics in cobalt nanoparticles directly influence mesoscopic resistance fluctuations.
• The mistracking effect provides a novel explanation for phase shifts in electron wave functions during domain wall traversal.
• Strong magnetocrystalline anisotropy contributes to the short dephasing time in cobalt nanoparticles at low temperatures.