Asymmetric I-V characteristics and magnetoresistance in magnetic point contacts

TL;DR

This paper theoretically investigates the transport properties of magnetic atomic-scale point contacts, revealing how domain wall positioning influences I-V symmetry and magnetoresistance, with potential diode-like behavior emerging without structural asymmetry.

Contribution

It introduces a self-consistent tight-binding model combined with non-equilibrium Green's functions to analyze electronic effects on magnetoresistance and I-V symmetry in magnetic point contacts.

Findings

Large magnetoresistance can occur due to electronic effects with a domain wall inside the contact.

The I-V characteristic symmetry depends on the domain wall position.

Off-center domain walls can produce diode-like I-V curves without structural asymmetry.

Abstract

We present a theoretical study of the transport properties of magnetic point contacts under bias. Our calculations are based on the Keldish's non-equilibrium Green's function formalism combined with a self-consistent empirical tight-binding Hamiltonian, which describes both strong ferromagnetism and charging effects. We demonstrate that large magnetoresistance solely due to electronic effects can be found when a sharp domain wall forms inside a magnetic atomic-scale point contact. Moreover we show that the symmetry of the $I$-$V$ characteristic depends on the position of the domain wall in the constriction. In particular diode-like curves can arise when the domain wall is placed off-center within the point contact, although the whole structure does not present any structural asymmetry.