Spin State of Single Molecular Magnet (SMM) Creating Long Range Ordering on Ferromagnetic Layers of Magnetic Tunnel Junction -A Monte Carlo Study

TL;DR

This study uses Monte Carlo simulations to explore how the spin state of single molecular magnets influences long-range magnetic ordering in ferromagnetic layers within magnetic tunnel junctions, revealing the importance of molecular coupling strength.

Contribution

It introduces a Monte Carlo simulation approach to analyze the effect of molecular spin states on ferromagnetic ordering in MTJ-based spintronics devices, highlighting the role of coupling strength.

Findings

Strong coupling regime requires molecular spin to be about 30% of ferromagnetic spins.

Molecular spin state significantly affects the spatial distribution of correlated magnetic phases.

Long-range order can be induced by tuning molecular coupling and spin states.

Abstract

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.