Quantum transport in ferromagnetic Permalloy nanostructures

TL;DR

This study investigates quantum coherence effects in mesoscopic Permalloy nanostructures at low temperatures, revealing conductance fluctuations, phase coherence length, and electron-electron interaction effects, but not weak localization.

Contribution

It provides the first detailed measurement of phase coherence length and conductance fluctuations in Permalloy nanostructures at millikelvin temperatures.

Findings

Phase coherence length of ~250 nm at 25 mK.

Conductance fluctuations exhibit a 1/√T temperature dependence.

Electron-electron interactions influence conductance, but weak localization signatures are absent.

Abstract

We studied phase coherent phenomena in mesoscopic Permalloy samples by exploring low temperature transport. Both, differential conductance as a function of bias voltage and magnetoconductance of individual wires display conductance fluctuations. Analysis of these fluctuations yields a phase coherence length of $\sim250$ nm at 25 mK as well as a $1/\sqrt{T}$ temperature dependence. To suppress conductance fluctuations by ensemble averaging we investigated low temperature transport in wire arrays and extended Permalloy films. In these samples we have measured conductance corrections which stem from electron-electron interaction (EEI) but attempts to detect signatures of weak localization were without success.