Magnetic Energy Landscape of Dimolybdenum Tetraacetate on a Bulk Insulator Surface

Abstract

The magnetic states and the magnetic anisotropy barrier of a transition metal molecular \ncomplex, dimolybdenum tetraacetate, are investigated via density functional theory (DFT). \nCalculations are performed in the gas phase and on a calcite (10.4) bulk insulating surface, using \nthe Generalized-Gradient Approximation (GGA)-PBE and the Hubbard-corrected DFT + U and \nDFT + U + V functionals. The molecular complex (denoted MoMo) contains two central metallic \nmolybdenum atoms, embedded in a square cage of acetate groups. Recently, MoMo was observed to \nform locally regular networks of immobile molecules on calcite (10.4), at room conditions. As this is \nthe first example of a metal-coordinated molecule strongly anchored to an insulator surface at room \ntemperature, we explore here its magnetic properties with the aim to understand whether the system \ncould be assigned features of a single molecule magnet (SMM) and could represent the basis to \nrealize stable magnetic networks on insulators. After an introductory review on SMMs, we show that, \nwhile the uncorrected GGA-PBE functional stabilizes MoMo in a nonmagnetic state, the DFT + U \nand DFT + U + V approaches stabilize an antiferromagnetic ground state and several meta-stable \nferromagnetic and ferrimagnetic states. Importantly, the energy landscape of magnetic states remains \nalmost unaltered on the insulating surface. Finally, via a noncollinear magnetic formalism and a \nnewly introduced algorithm, we calculate the magnetic anisotropy barrier, whose value indicates the \nstability of the molecule’s magnetic moment.