Ferromagnetism appears in nitrogen implanted nanocrystalline diamond films

• Nitrogen implanted nanocrystalline diamond films exhibit ferromagnetism at room temperature.
• Nitrogen implants made a Raman deviation from the typical nanocrystalline diamond films.
• The ferromagnetism induced from the structure distortion is dominant at low temperature.

The nanocrystalline diamond films turn to be ferromagnetic after implanting various nitrogen doses on them. Through this research, we confirm that the room-temperature ferromagnetism of the implanted samples is derived from the measurements of magnetic circular dichroism (MCD) and superconducting quantum interference device (SQUID). Samples with larger crystalline grains as well as higher implanted doses present more robust ferromagnetic signals at room temperature. Raman spectra indicate that the small grain-sized samples are much more disordered than the large grain-sized ones. We propose that a slightly large saturated ferromagnetism could be observed at low temperature, because the increased localization effects have a significant impact on more disordered structure.