Magnetic phenomena in 5d transition metal nanowires

TL;DR

This study uses relativistic density-functional calculations to explore magnetic properties of 5d transition metal nanowires, revealing potential for spin-polarized conductance and superparamagnetism in certain metals.

Contribution

It provides the first detailed relativistic analysis of magnetic phenomena in 5d transition metal nanowires, highlighting conditions for spin polarization.

Findings

Os and Pt nanowires exhibit magnetic moments at equilibrium bond lengths.

Au and Ir nanowires become spin-polarized when slightly stretched.

Superparamagnetic states influence conductance and spin polarization.

Abstract

We have carried out fully relativistic full-potential, spin-polarized, all-electron density-functional calculations for straight, monatomic nanowires of the 5d transition and noble metals Os, Ir, Pt and Au. We find that, of these metal nanowires, Os and Pt have mean-field magnetic moments for values of the bond length at equilibrium. In the case of Au and Ir, the wires need to be slightly stretched in order to spin polarize. An analysis of the band structures of the wires indicate that the superparamagnetic state that our calculations suggest will affect the conductance through the wires -- though not by a large amount -- at least in the absence of magnetic domain walls. It should thus lead to a characteristic temperature- and field dependent conductance, and may also cause a significant spin polarization of the transmitted current.