Anisotropic magnetoresistance in ferromagnetic atomic-sized metal contacts

TL;DR

This paper provides a theoretical analysis of anisotropic magnetoresistance (AMR) in ferromagnetic atomic contacts, explaining enhanced effects and asymmetry due to reduced symmetry and impurities.

Contribution

It introduces a theoretical framework linking atomic contact geometry and impurities to the observed AMR phenomena in ferromagnetic materials.

Findings

AMR is enhanced and asymmetric in atomic contacts.

Reduced symmetry of contact geometries causes anomalous AMR.

Impurities near constrictions influence voltage and temperature dependence.

Abstract

Recent experiments in ferromagnetic atomic-sized contacts have shown that the anisotropic magnetoresistance (AMR) is greatly enhanced and has an asymmetric angular dependence as compared with that of bulk samples. The origin of these effects is still under debate. In this work we present a theoretical analysis of the AMR in atomic contacts of the 3d ferromagnetic materials. Our results strongly suggest that the anomalous AMR stems from the reduced symmetry of the atomic contact geometries. We also present calculations supporting the idea that the pronounced voltage- and temperature dependence in some experiments can be attributed to impurities near the constrictions.