  Molecular spintronics devices (MSDs) are highly promising candidates for
enabling quantum computation and revolutionizing computer logic and memory. An
advanced MSD will require the placement of magnetic molecules between the two
ferromagnetic (FM) electrodes. Recent experimental studies showed that some
magnetic molecules produced unprecedented strong exchange couplings between the
two FM electrodes leading to intriguing magnetic and transport properties in a
MSD. Future development of MSDs will critically depend on obtaining an in-depth
understanding of the molecule induced exchange coupling, and its impact on
switchability, functional temperature range, and stability. However, the large
size of MSD systems and fragile device fabrication scheme continue to limit the
theoretical and experimental studies of magnetic attributes produced by
molecules in a MSD. This paper theoretically studies the MSD by performing
Monte Carlo simulations (MCS). Our MCS encompasses the full range of MSDs that
can be realized by establishing different kinds of magnetic interaction between
magnetic molecules and FM electrodes. Our MSDs are represented by a 2D Ising
model. We studied the effect of a wide range of molecule-FM electrode couplings
on the basic properties of MSDs. This wide range covered (i) molecule
possessing ferromagnetic coupling with both FM electrodes, (ii) molecule
possessing antiferromagnetic coupling with both FM electrodes, and (iii)
molecule possessing ferromagnetic coupling with one electrode and
antiferromagnetic coupling with another FM electrode. Our MCS will enable the
fundamental understanding and designing of a wide range of novel MSDs utilizing
a variety of molecules and FM electrodes; these studies will also benefits
nanomaterials based spintronics devices employing nanoclusters and quantum dots
as the device elements.
