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Collaborative Research Realized Precise Control of Magnetic Ground States in Nanographenes

November 30, 2020      Author:

Recently, Special Researcher Wang Shiyong and Professor Jia Jinfeng from SJTU School of Physics and Astronomy published their latest research results"Designer spin order in diradical nanographenes" in collaboration with Professor Feng Xinliang from Dresden University of Technology in Nature Communications, an internationally renowned journal. Following the successful synthesis of atomic-level accurate and controllable magnetic nanographene structure (PhysRevLett.124.147206), the research group conducted an in-depth study on the magnetic exchange mechanism of π electrons in this system, and successfully realized the controllable transition between ferromagnetic ground state and antiferromagnetic ground state in π electron system. In addition, the antiferromagnetic coupling strength of up to 42meV is achieved by adjusting the overlap of the zero-energy wave functions of π electrons, which can be used to design spin electronic devices above room temperature. The findings can be applied to preparing more complex carbon-based magnetic structures, and then explore their quantum spin effects.

Doctoral students Zheng Yuqiang and Li Can are the co-first authors of this work. Special thanks to Professor Markus Ternes of Aachen University of Technology, Germany, for his contributions to the discussion, and to Liu Chen and other students for their help in the experiment.

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.

 

Author: Wang Shiyong

Affiliation: School of Physics and Astronomy

Translated by Zhou Rong