On magnetic nature of Mn clusters

Manganese atom having number of unpaired electrons appears as a strong building block for molecular magnets. This prompts the investigation of the magnetic behavior of Mn based clusters. In this work, we have studied the magnetic characteristics of neutral Mn dimer, charged Mn dimer and its oxide. The magnetic characteristics of the chosen systems have been quantified in terms of intramolecular exchange coupling constant. The computation is performed in the framework of density functional theory using broken symmetry approach. We obtain positive values of magnetic exchange coupling constants for all these three species and hence their ferromagnetic ground states are recognized. Direct exchange of spins between the sets of d-electrons in the metals is found responsible for the ferromagnetic behavior of these clusters. In case of Mn2O−, super exchange, another possible exchange mechanism, is barred due to unavailability of vacant metal d-orbitals. Dependence of exchange coupling constant on intermetallic distance is also studied taking these Mn clusters as reference, which shows a maximum value of coupling constant in the proximity of equilibrium bond distance.