Gate control of spin-polarized conductance in alloyed transition metal nano-contacts

TL;DR

This paper demonstrates that in metallic nano-contacts with magnetic chains, applying a gate voltage can control and even reverse the spin polarization of conductance, offering a new approach for spintronic device functionality.

Contribution

It introduces a purely metallic, gate-controlled method to manipulate spin-polarized conductance in atomic chains, expanding spintronics beyond semiconductor-based systems.

Findings

Gate bias shifts spin-polarized states in atomic chains.

Conductance spin-polarization strongly depends on gate potential.

Reversal of spin-polarization sign achieved with gate voltage.

Abstract

To date, endeavors in nanoscale spintronics are dominated by the use of single-electron or single-spin transistors having at their heart a semiconductor, metallic or molecular quantum dot who's localized states are non-spin-degenerate and can be controlled by an external bias applied via a gate electrode. Adjusting the bias of the gate one can realign those states with respect to the chemical potentials of the leads and thus tailor the spin-polarized transmission properties of the device. Here we show that similar functionality can be achieved in a purely metallic junction comprised of a metallic magnetic chains attached to metallic paramagnetic leads and biased by a gate electrode. Our ab initio calculations of electron transport through mixed Pt-Fe (Fe-Pd and Fe-Rh) atomic chains suspended between Pt (Pd and Rh) electrodes show that spin-polarized confined states of the chain can be shifted by the gate bias causing a change in the relative contributions of majority and minority channels to the nano-contact's conductance. As a result, we observe strong dependence of conductance spin-polarization on the applied gate potential. In some cases the spin-polarization of conductance can even be reversed in sign upon gate potential application, which is a remarkable and promising trait for spintronic applications.