A research team led by Prof. SUN Lianfeng from National Center for Nanoscience and Technology, China (NCNST), in collaboration with Prof. SUN Qing-Feng from Peking University, has discovered one-dimensional ferromagnetism along the edges formed between molybdenum (Mo) strips and monolayer graphene (MLG). The interface exhibits unique linear V or W-shaped anisotropic magnetoresistance and maintains spin Hall effects up to room temperature, demonstrating the coexistence of Kondo behavior and ferromagnetic order. The findings were published in Nano Today.

Low-dimensional magnetic systems have attracted broad interest for fundamental research and future electronic devices. Although two-dimensional magnets have been reported, achieving magnetic order in one-dimensional structures remains challenging due to theoretical limitations. The Mermin-Wagner theorem forbids magnetic order in one-dimensional isotropic systems, but this restriction can be overcome by magnetic anisotropy or structural confinement.

To address this challenge, the team developed a Mo/graphene heterostructure system. When a molybdenum strip is deposited across monolayer graphene using magnetron sputtering, a solid-state reaction removes the graphene beneath the Mo, creating two clean one-dimensional edges. These edges host localized magnetic moments, evidenced by the observation of the Kondo effect which is a characteristic resistance increase at low temperatures due to scattering from magnetic impurities.

The team further identified unique linear V or W-shaped anisotropic magnetoresistance under small magnetic fields, a signature of one-dimensional ferromagnetism. When two parallel Mo strips were fabricated on the same graphene sheet, the researchers not only observed Kondo effect and anisotropic magnetoresistance but also detected spin Hall effect and inverse spin Hall effect at temperatures up to 300 K. These results indicate antiferromagnetic coupling between the two edges and efficient spin-charge conversion at room temperature.

This Mo/MLG system provides a highly controllable platform for studying low-dimensional magnetism and developing energy-efficient spintronic devices.

Contact: SUN Lianfeng

National Center for Nanoscience and Technology (NCNST)

E-mail: slf@nanoctr.cn