  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.
