Dynamical Negative Differential Resistance in Antiferromagnetically Coupled Few-Atom Spin-Chains

TL;DR

This study demonstrates negative differential resistance in a few-atom spin-chain system caused by dynamic spin locking during electron tunneling, revealing interplay between transport and magnetic interactions at the atomic scale.

Contribution

It reports the first observation of NDR in a spin-dependent electron transport through an antiferromagnetically coupled atomic spin chain, highlighting dynamic spin locking effects.

Findings

NDR appears at low bias of 7 mV due to spin locking.

Dynamic locking competes with magnetic exchange interaction.

Varying tip coupling affects the NDR and magnetic states.

Abstract

We present the appearance of negative differential resistance (NDR) in spin-dependent electron transport through a few-atom spin-chain. A chain of three antiferromagnetically coupled Fe atoms(Fe trimer) was positioned on a Cu2N/Cu(100) surface and contacted with the spin-polarized tip of a scanning tunneling microscope, thus coupling the Fe trimer to one non-magnetic and one magnetic lead. Pronounced NDR appears at the low bias of 7 mV where inelastic electron tunneling dynamically locks the atomic spin in a long-lived excited state. This causes a rapid increase of the magnetoresistance between spin-polarized tip and Fe trimer and quenches elastic tunneling. By varying the coupling strength between tip and Fe trimer we find that in this transport regime the dynamic locking of the Fe trimer competes with magnetic exchange interaction, which statically forces the Fe trimer into the high-magnetoresistance state and removes the NDR.