From ballistic transport to tunneling in electromigrated ferromagnetic breakjunctions

TL;DR

This study demonstrates the transition from ballistic transport to tunneling in electromigrated ferromagnetic breakjunctions, revealing significant changes in magnetoresistance as the constriction narrows to atomic scales.

Contribution

It introduces a method to gradually reduce ferromagnetic nanowire constrictions to atomic scales and measures the resulting magnetoresistance changes, highlighting the transition from ballistic to tunneling regimes.

Findings

Magnetoresistance increases from ~0.3% to 80% as constriction narrows.

Large MR fluctuations observed in the tunneling regime, between -10% and 85%.

Devices are mechanically stable and suitable for studying transport regimes.

Abstract

We fabricate ferromagnetic nanowires with constrictions whose cross section can be reduced gradually from 100 nm to the atomic scale and eventually to the tunneling regime by means of electromigration. These devices are mechanically stable against magnetostriction and magnetostatic effects. We measure magnetoresistances ~ 0.3% for 100*30 nm^2 constrictions, increasing to a maximum of 80% for atomic-scale widths. These results are consistent with a geometrically-constrained domain wall trapped at the constriction. For the devices in the tunneling regime we observe large fluctuations in MR, between -10 and 85%.