Growth mode and structures of magnetic Mn clusters on graphene

We present a systematic study of Mn clusters on graphene by first-principles calculations. We show that the growth of Mn on graphene follows a three-dimensional (3D) mode. Both adsorption and attachment energies show that (Mn)3 and (Mn)6 on graphene are energetically favorable in the size range (Mn)1–7. Moreover, the larger formation energy for Mn clusters on graphene implies that the incoming Mn atoms are likely to nucleate and grow into bigger and bigger Mn clusters on graphene. The magnetic moments of (Mn)1,5,7 on graphene are enhanced by 11%, 186%, and 26% from their values at free-standing clusters, respectively. By contrast, the net magnetic moment of (Mn)2,3,4,6 on graphene is reduced from that of the corresponding free-standing clusters. The origin of the magnetic moment changes can be attributed to the charge transfer within the Mn clusters and between the clusters and graphene upon adsorption.