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

Abstract

This paper reports our Monte Carlo (MC) studies aiming to explain the experimentally observed paramagnetic molecule induced antiferromagnetic coupling between ferromagnetic (FM) electrodes. Recently developed magnetic tunnel junction based molecular spintronics devices (MTJMSDs) were prepared by chemically bonding the paramagnetic molecules between the FM electrodes along the tunnel junction's perimeter. These MTJMSDs exhibited molecule-induced strong antiferromagnetic coupling. We simulated the 3D atomic model analogous to the MTJMSD and studied the effect of molecule's 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. Our studies suggest that in order to align MTJMSDs' electrodes antiparallel to each other, the exchange coupling strength between a molecule and FM electrodes should be ∼50% of the interatomic exchange coupling for the FM electrodes.

Large resistance change on magnetic tunnel junction based molecular spintronics devices

“…However, we also noted that FMR response from the MTJ with Ta ( Fig. 5b) and without Ta on top [8] were very different. The further exploration about Ta role will be part of future study and beyond the scope of this paper.…”

“…1i-k. The experimental details for SQUID magnetometer and FMR studies are discussed elsewhere [8]. SQUID study showed that the magnetic moment of the MTJ Fig.…”

“…To date most of the experimental studies have only focused on the transport studies-no direct magnetic measurements were performed [3,4,7]. To overcome the limitations of the conventional molecular spintronics devices magnetic tunnel junctions (MTJ), produced by sandwiching an insulator between two ferromagnetic electrodes, were utilized as the test bed [5,6,8]. Under this approach an MTJ with the exposed side edges can enables the covalent bonding of desired molecular channels onto the two ferromagnetic electrodes along the junction perimeter [5].…”

“…SQUID and ferromagnetic resonance were performed as per the details furnished elsewhere [8]. (e) Liftoff step produces an MTJ with the exposed sides where (f) OMC molecules are chemically bridged across the AlOx insulator to produce an MTJMSD.…”

Magnetic force microscopy revealing long range molecule impact on magnetic tunnel junction based molecular spintronics devices

“…10 chemical structure. The exposed side edge of an MTJ was produced by the previously published liftoff based molecular device fabrication method 6,11 . In this study, the MTJ with Ta(5 nm)/Co(5-7 nm)/NiFe(5-3 nm)/AlOx(2 nm)/NiFe (10 nm) configuration was utilized.…”