  Single molecular magnet (SMM) like paramagnetic molecules interacting with
the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) produce a new
system that differs dramatically from the properties of isolated molecules and
ferromagnets. However, it is unknown how far deep in the ferromagnetic
electrode the impact of the paramagnetic molecule and ferromagnet interactions
can travel for various levels of molecular spin states. Our prior experimental
studies showed two types of paramagnetic SMMs, the hexanuclear Mn6 and
octanuclear Fe-Ni molecular complexes, covalently bonded to ferromagnets
produced unprecedented strong antiferromagnetic coupling between two
ferromagnets at room temperature leading to a number of intriguing
observations. In this paper, we report Monte Carlo Simulations (MCS) study
focusing on the impact of the molecular spin state on cross junction shaped MTJ
based molecular spintronics device (MTJMSD). Our MCS study focused on the
Heisenberg model of MTJMSD and investigated the impact of various molecular
coupling strengths, thermal energy, and molecular spin states. To gauge the
impact of the molecular spin state on the region of ferromagnetic electrodes,
we examined the spatial distribution of molecule-ferromagnet correlated phases.
Our MCS study shows that under a strong coupling regime molecular spin state
should be approximately 30 percent of the ferromagnetic electrode atomic spins
to create long-range correlated phases.
