Fe₄ cluster as the smallest 3D Fe cluster with unique quantum magnetic levitation effect on graphene

The unique quantum magnetic levitation effect of small metallic clusters adsorbed on graphene has been studied for their minimal energy configurations in this work. Using first-principles calculations, we specially focus on the tetrahedral Fe₄ clusters in a corn-like configuration for the induced magnetic moments in the Fe₄ cluster and graphene. Firstly, the 3D magnetic Fe₄ cluster spontaneously induced a diamagnetic moment in graphene in the absence of external energy injection. Additionally, as the smallest 3D particle (among Fe_n clusters), the Fe₄ cluster can be levitated by the repulsive magnetic interaction between the Fe cluster and graphene. The maximum energy barrier between different adsorption configurations of the Fe₄ cluster on graphene is as low as 0.8 eV, making the Fe₄ cluster diffusible between sites with a minimal external force. The conversion energy barrier is relatively low, resulting in low energy consumption. Importantly, the repulsion between Fe clusters may lead to the formation of an ultrahigh-density (1.18 × 10¹⁴/cm²) isolated quantum dot array and avoids the formation of larger clusters. These quantum states might be usable for nanoscale data storage devices for next-generation computing applications, and the small diffusion barrier might offer potential applications in quantum mechanical sensing and nanoscale magnetic levitation. © 2023 Elsevier B.V.