Ferromagnetism in homogeneous (Al,Co)-codoped 4H-silicon carbides

• High-quality (Al, Co)-codoped 4H-SiC are synthesized via solid state reaction.
• Doping element Al and Co are proved to be the origin for the observed magnetism.
• Ferromagnetism may originate from a composite mechanism.
• Annoying issues including SiC polytypes and magnetic secondary phases were solved.

In view of the recent controversies on above room-temperature (RT) ferromagnetism (FM) in transition-metal (TM) doped silicon carbides (SiC), the present paper aims to shed some light on the natural origin of long-range magnetic order by investigating the (Al, Co)-doped 4H-SiC, both experimentally and theoretically. A combination of characterizations means including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and X-ray absorption near-edge structure spectroscopy (XANES) measurement eliminated the presence of any nanoclusters or secondary phases as the source of FM. X-ray absorption near-edge structure spectroscopy analyses provided convincing evidence that no secondary phases such as Co metallic clusters were present when Co and Al are homogeneously inserted in the SiC matrix. RT FM originates from a composite mechanism based on the Ruderman–Kittel–Kasuya–Yosida, and double-exchange interactions. The dopant Al is found to stabilize the crystal structure as well as show the experimental possibility of tuning the magnetization by codoping.