Magnetoresistance of mesoscopic granular ferromagnets

TL;DR

This study investigates the magnetoresistance properties of small-scale granular ferromagnets, revealing unique behaviors and a transition in conduction mechanisms as grain connectivity changes.

Contribution

It provides new insights into the magnetoresistance behavior of mesoscopic granular ferromagnets and identifies a transition from percolation to single-channel transport.

Findings

Large saturation fields and MR amplitudes in small samples

Distinct evolution of MR curves with decreasing intergrain distance

Evidence of a transition from percolation to single-channel conduction

Abstract

We have performed magnetoresistance (MR) measurements of granular ferromagnets having lateral dimensions smaller than 0.5 $\mu$m and containing a small number of grains (down to about 100). Compared to macroscopic samples, these granular samples exhibit unusually large saturation fields and MR amplitudes. In addition, the evolution of the magnetoresistance curve as the intergrain distance decreases is qualitatively different than that of large samples. We discuss these results and suggest that they reflect a transition from percolation to quasi single-channel dominated transport.