Abstract
The magnetic properties of carbon materials are at present the focus of intense research effort in physics, chemistry and materials science due to their potential applications in spintronics and quantum computing. Although the presence of spins in open-shell nanographenes has recently been confirmed, the ability to control magnetic coupling sign has remained elusive but highly desirable. Here, we demonstrate an effective approach of engineering magnetic ground states in atomically precise open-shell bipartite/nonbipartite nanographenes using combined scanning probe techniques and mean-field Hubbard model calculations. The magnetic coupling sign between two spins was controlled via breaking bipartite lattice symmetry of nanographenes. In addition, the exchange-interaction strength between two spins has been widely tuned by finely tailoring their spin density overlap, realizing a large exchange-interaction strength of 42 meV. Our demonstrated method provides ample opportunities for designer above-room-temperature magnetic phases and functionalities in graphene nanomaterials.
Highlights
The magnetic properties of carbon materials are at present the focus of intense research effort in physics, chemistry and materials science due to their potential applications in spintronics and quantum computing
We recently demonstrated that nanographenes with such pentagon rings host net spins and the coupling strength can be engineered by tailoring spin density overlap at the connecting region[30]
Mean-field Hubbard model and spin-polarized density functional theory (SP-DFT) calculations confirm the presence of one unpaired electron with enhanced spin density distribution at the right side
Summary
The magnetic properties of carbon materials are at present the focus of intense research effort in physics, chemistry and materials science due to their potential applications in spintronics and quantum computing. Incorporation of a pentagon into a magnetic diradical NG drives the ferromagnetic coupled ground state into antiferromagnetic coupled ground state The nature behind this exchange interaction, as we have revealed, is a local reversal of spin density sign at the connecting region of the dimer via breaking the bipartite lattice symmetry of NGs. The nature behind this exchange interaction, as we have revealed, is a local reversal of spin density sign at the connecting region of the dimer via breaking the bipartite lattice symmetry of NGs This exchange mechanism is expected to be generic and widespread, because it relies solely on very general features of the nonbipartite character of NGs. since it is feasible to precisely tailor the chemical structure of NGs by using on-surface synthesis, the established approach can be extended to design any artificial quantum spin systems, opening wide possibility for fundamental research and applications in spintronics and quantum information technologies
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