Magnetoresistance of atomic-scale electromigrated nickel nanocontacts

TL;DR

This study investigates electron transport in atomic-scale nickel nanocontacts, revealing increased anisotropic magnetoresistance at small scales and mesoscopic variations, with no large ballistic effects observed.

Contribution

It demonstrates how magnetoresistance behaviors evolve at atomic scales in ferromagnetic nanocontacts, combining fabrication techniques with detailed transport measurements.

Findings

AMR increases as junction size decreases

Magnetoresistance shows mesoscopic variations in magnitude and sign

No evidence of large ballistic magnetoresistance effects

Abstract

We report measurements of the electron transport through atomic-scale constrictions and tunnel junctions between ferromagnetic electrodes. Structures are fabricated using a combination of e-beam lithography and controlled electromigration. Sample geometries are chosen to allow independent control of electrode bulk magnetizations. As junction size is decreased to the single channel limit, conventional anisotropic magnetoresistance (AMR) increases in magnitude, approaching the size expected for tunneling magnetoresistance (TMR) upon tunnel junction formation. Significant mesoscopic variations are seen in the magnitude and sign of the magnetoresistance, and no evidence is found of large ballistic magnetoresistance effects.