Magnetism and superconductivity in amorphous carobn

We study magnetic and superconducting properties of amorphous carbon based on molecular dynamics simulations. First we use spin constrained first-principles simulations to obtain amorphous carbon structures with a desired magnetization. We show that the existence of sp²-like threefold coordinated carbon atoms plays an important role in causing magnetism in amorphous carbon. We predict detailed geometries of threefold carbon atoms that induce the magnetic order in amorphous carbon. We also consider the effect of boron doping on superconducting properties of amorphous carbon. By considering amorphous structures with various sp²:sp³ ratios, we find that sp³-hybridized atoms are necessary for high superconducting transition temperature in contrast to the magnetism.