Paramagnetic molecule induced strong antiferromagnetic exchange coupling on a magnetic tunnel junction based molecular spintronics device

TL;DR

This study uses Monte Carlo simulations to explain how paramagnetic molecules induce strong antiferromagnetic exchange coupling in magnetic tunnel junction-based molecular spintronics devices, aligning with experimental observations.

Contribution

It demonstrates that specific magnetic couplings between molecules and electrodes can explain the observed antiferromagnetic interactions in these devices.

Findings

Molecular coupling with electrodes can induce antiferromagnetic interactions.

The strength of molecule-electrode exchange coupling should be about 50% of interatomic exchange.

Simulations match experimental results when molecules have mixed ferromagnetic and antiferromagnetic couplings.

Abstract

This paper reports our Monte Carlo (MC) studies aiming to explain the experimentally observed paramagnetic molecule induced antiferromagnetic coupling between the ferromagnetic (FM) electrodes. Recently developed magnetic tunnel junction based molecular spintronics devices (MTJMSDs), which were prepared by chemically bonding the paramagnetic molecules between the FM electrodes along the exposed side edges of magnetic tunnel junctions, exhibited molecule induced strong antiferromagnetic coupling. Our MC studies focused on the atomic model analogous to the MTJMSD and studied the effect of molecules magnetic couplings with the two FM electrodes. Simulations show that when a molecule established ferromagnetic coupling with one electrode and antiferromagnetic coupling with the other electrode then theoretical results effectively explained the experimental findings. MC and experimental studies suggest that the strength of exchange coupling between molecule and FM electrode should be 50 percent of the interatomic exchange coupling strength of the FM electrodes.