Mesoscopic Resistance Fluctuations in Cobalt Nanoparticles

TL;DR

This study investigates mesoscopic resistance fluctuations in cobalt nanoparticles, revealing how domain-wall dynamics and spin mistracking influence electron phase shifts and dephasing at very low temperatures.

Contribution

It demonstrates the impact of domain-wall nucleation and annihilation on resistance fluctuations and identifies spin mistracking as the cause of phase shifts, with measurements at ultra-low temperatures.

Findings

Domain-wall causes an electron wavefunction phase-shift of approximately 5π.

Bias fingerprints rearrange during magnetization reversal.

Dephasing time in Co at 0.03K is about picoseconds.

Abstract

We present measurements of mesoscopic resistance fluctuations in cobalt nanoparticles and study how the fluctuations with bias voltage, bias fingerprints, respond to magnetization reversal processes. Bias fingerprints rearrange when domains are nucleated or annihilated. The domain-wall causes an electron wavefunction phase-shift of $\approx 5\pi$. The phase-shift is not caused by the Aharonov-Bohm effect; we explain how it arises from the mistracking effect, where electron spins lag in orientation with respect to the moments inside the domain-wall. Dephasing time in Co at $0.03K$ is short, $\tau_\phi\sim ps$, which we attribute to the strong magnetocrystalline anisotropy.