Mechanically tunable magnetism on graphene nanoribbon adsorbed SiO ₂ surface

Our first-principle calculations reveal that the O-terminated surface of zigzag graphene nanoribbon adsorbed (100) α-quartz SiO ₂ exhibits antiferromagnetic ground state. This is due to unpaired electrons of dangling O atoms forming on the SiO ₂ surface, which are caused by the edge C atoms of the adsorbed nanoribbon. The resulting magnetism and spin-resolved states on the SiO ₂ surface can be effectively tuned by mechanical strain applied on the substrate, with the antiferromagnetic state transforming into ferromagnetic state as well as the total magnetic moment varying from negative to positive when the strain turns from tensile to compressive. We elucidate the mechanism for the modification of the surface magnetism by orbital hybridization between C and O atoms and part of dangling O atoms bonding with the nanoribbon under strain.