Magnetoresistance ratio of a point-like contact with a 1 nm wide domain wall at different MFP asymmetries

TL;DR

This paper develops a unified theoretical model for spin-resolved electron transport in nanoscale magnetic point contacts, analyzing how magnetoresistance varies with contact size, spin asymmetry, and material parameters, revealing potential for efficient magnetic sensing.

Contribution

It introduces a seamless model bridging ballistic and diffusive regimes for magnetic point contacts without empirical fitting, enhancing understanding of magnetoresistance behavior at the nanoscale.

Findings

Magnetoresistance strongly depends on contact size and spin asymmetry.

MR can become negative at certain contact sizes and parameters.

Nanoscale magnetic PCs show high efficiency for magnetic sensing applications.

Abstract

This work presents a unified theoretical framework for spin-resolved electron transport in magnetic point contacts (PCs) in nanoscale dimensions. This work advances existing research by presenting a model which seamlessly transitions between Sharvin ballistic and Maxwell-Holm diffusive limits across the wide range of relevant contact sizes without incorporating empirical fitting factors. We analyzed the magnetoresistance (MR) of magnetic PCs formed with two ferromagnetic monodomains that may have parallel and antiparallel magnetization alignment, forming a constrained domain wall approximately 1.0 nm wide. The calculated MR exhibits strong dependence on scaling parameter (normalized contact radius), ratios of spin-dependent mean free paths, and Fermi wave-vectors. Furthermore, the calculated MR exhibits physically meaningful behavior over a wide range of spin-asymmetry parameters. In most regimes, the MR decreases with increasing normalized point-contact radius, becoming negative at some conditions. These results demonstrate that nanoscaled magnetic PCs have great efficiency in terms of magnetoresistnace change and promising for application due to their simplicity.