Competing magnetic anisotropies in atomic-scale junctions

TL;DR

This study uses first-principles calculations to explore how stretching atomic-scale W, Ir, and Pt junctions influences their magnetic properties, revealing large anisotropy energies and magnetization axis switches observable experimentally.

Contribution

It provides new insights into the magnetic behavior of 5d transition-metal atomic junctions under elongation, including the prediction of magnetization axis switches and the role of local symmetry.

Findings

Strong magnetism develops upon stretching the chains.

Large magnetocrystalline anisotropy energies up to 30 meV per atom.

Switches in easy magnetization axis are predicted to be observable.

Abstract

Using first-principles calculations, we study the magnetism of 5d transition-metal atomic junctions including structural relaxations and spin-orbit coupling. Upon stretching monatomic chains of W, Ir, and Pt suspended between two leads, we find the development of strong magnetism and large values of the magnetocrystalline anisotropy energy (MAE) of up to 30 meV per chain atom. We predict that switches of the easy magnetization axis of the nanocontacts upon elongation should be observable by ballistic anisotropic magnetoresistance measurements. Due to the different local symmetry, the contributions to the MAE of the central chain atoms and chain atoms in the vicinity of the leads can have opposite signs which reduces the total MAE. We demonstrate that this effect occurs independent of the chain length or geometry of the electrodes.