Single-molecule magnetMn12on graphene

Abstract

We study energetics, electronic and magnetic structures, and magnetic anisotropy barriers of a monolayer of single-molecule magnets (SMM), [Mn 12 O 12 (COOR) 16 ](H 2 O) 4 (abbreviated as Mn 12 , with R=H, CH 3 , C 6 H 5 and CHCl 2 ), on a graphene surface using spin-polarized density-functional theory with generalized gradient corrections and the inclusion of van der Waals interactions. We find that Mn 12 molecules with ligands -H, -CH 3 , and -C 6 H 5 are physically adsorbed on graphene through weak van der Waals interactions, and a much stronger ionic interaction occurs using a -CHCl 2 ligand. The strength of bonding is closely related to the charge transfer between the molecule and the graphene sheet and can be manipulated by strain in the graphene; specifically, tension enhances n-doping of graphene and compression encourages p-doping. The magnetic anisotropy barrier is computed by including the spin-orbit interaction within density-functional theory. The barriers for the Mn 12 molecules with ligands -H, -CH 3 and -C 6 H 5 on graphene surfaces remain unchanged (within 1 K) from those of isolated molecules because of their weak interaction, and a much larger reduction (10 K) is observed when using the -CHCl 2 ligand on graphene due to a substantial structural deformation as a consequence of the much stronger interaction. Neither strain in graphene nor charge transfer affects the magnetic anisotropy barrier significantly. Finally, we discuss the effect of strong correlation in the high spin state of a Mn 12 SMM and the consequence in SMM-surface adsorption.

Designing a highly efficient graphene quantum spin heat engine

“…There should not be much difficulty in realizing strain in a graphene system. In addition, there are theoretical works which deal with effects of magnetic impurities on electronic transport in graphene, see refs 26,32,33,45,46 . In ref.…”

Molecular analogue of the perovskite repeating unit and evidence for direct MnIII-CeIV-MnIII exchange coupling pathway

“…To characterize the origin of the AF ground state of Ce 3 Mn 8 , the magnetic properties of Ce 3 Mn 8 were calculated within the framework of Kohn–Sham density functional theory (DFT), using atomic coordinates for the molecule taken from the crystal structure. DFT based methods have been widely used for studying molecular magnets with Mn centers 26 – 31 . First-principles calculations were performed for eight different spin configurations of Ce 3 Mn 8 molecules, corresponding to FM, A-AF, C-AF, and G-AF spin alignments ( Supplementary Methods ), with all three orientations of the ferromagnetic planes (A-AF) or axes (C-AF) considered and neglecting any noncolinearity (the easy axis is assumed to be along the global z axis).…”

First-principles study of magnetism and electric field effects in 2D systems

“…It was shown that charging is an effective way to tune the magnetic anisotropy of a magnetic molecule; 107 and we have previously simulated the electron transfer between graphene and Mn 12 molecules without a gate field. 108 Following this thread, we started investigations to address how charge doping affects the magnetic anisotropy of single-molecule magnets such as Mn 12 . A glance in the field of first-principles transport studies, there is very little theoretical work 109,110 addressing the role of spin-orbit coupling of molecules or 2D junction under finite gate or bias voltages.…”