Giant Anisotropic Magneto-Resistance in ferromagnetic atomic contacts

TL;DR

This paper demonstrates that anisotropic magneto-resistance is significantly enhanced in atomic-sized ferromagnetic contacts due to spin-orbit coupling effects, with ab-initio calculations supporting the physical mechanism.

Contribution

It reveals the enhanced anisotropic magneto-resistance at atomic scales and explains it through changes in electronic density of states caused by spin-orbit coupling.

Findings

Enhanced anisotropic magneto-resistance in atomic contacts

Spin-orbit coupling influences conductance at atomic scale

Ab-initio calculations support the physical explanation

Abstract

Magneto-resistance is a physical effect of great fundamental and industrial interest since it is the basis for the magnetic field sensors used in computer read-heads and Magnetic Random Access Memories. As device dimensions are reduced, some important physical length scales for magnetism and electrical transport will soon be attained. Ultimately, there is a strong need to know if the physical phenomena responsible for magneto-resistance still hold at the atomic scale. Here, we show that the anisotropy of magneto-resistance is greatly enhanced in atomic size constrictions. We explain this physical effect by a change in the electronic density of states in the junction when the magnetization is rotated, as supported by our ab-initio calculations. This stems from the "spin-orbit coupling" mechanism linking the shape of the orbitals with the spin direction. This sensitively affects the conductance of atomic contacts which is determined by the overlap of the valence orbitals.