"These findings could lead to a systematic, controllable method for producing magnetic carbon materials," said Pulickel Ajayan of Rensselaer. "Though the value of the magnetization is much lower than in regular magnets, the nature of the spin interactions in carbon could lead to a number of potential applications."
Magnetic carbon nanostructures could have applications in high-density memory devices, quantum computers and, since carbon is generally biocompatible, magnetic resonance imaging and targeted drug delivery.
"Carbon is lightweight, very stable, simple to process and less expensive [than metals] to produce," said Saikat Talapatra of Rensselaer.
To create the structures, Talapatra, Ajayan and colleagues implanted 15N or 12C ions into nanodiamond particles with an average diameter of 4 - 5 nm. The treated nanodiamonds displayed ferromagnetic behaviour: the scientists believe this was a result of the ions causing defects and irregularities that produced unpaired electrons.
For lower doses of ions (less than 1014 cm-2), both nitrogen and carbon ions produced similar magnetizations. The researchers say this indicates that the magnetization arises mainly from structural deformation of the carbon bonds.
But above this dose, the nitrogen ion-doped samples had a higher saturation magnetization than the carbon ion-doped particles. The team says this could be due to extensive defect generation or graphitization, and also to incorporation of nitrogen in the graphitic network and the formation of C-N bonds.
According to the researchers, the next step is to calculate how the types of defects and their concentration affect the magnitude of the magnetism created.
"We are also working toward developing simpler ways to make magnetic nanocarbons in a more controlled fashion," said Talapatra. "The long-term goal is to show some real applications using these structures."
The researchers reported their work in Physical Review Letters.