New nanoparticles are provided which may have blocking temperatures exceeding 570 K even for particles as small as 8 nm in size. First principles theoretical investigations show that the new behavior is rooted in the giant magnetocrystalline anisotropies due to controlled mixing between carbon p-states and cobalt d-states. Furthermore, assemblies of the new nanoparticles may provide rare earth free permanent magnets having magnetic properties which rival those of rare earth permanent magnets.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with government support under Grant No. 0472-1574 awarded by the Advanced Research Projects Agency (ARPA), MRI Grants No. CHE0820945 and No. CHE0922582 awarded by National Science Foundation, and Grant No. 0472-1572 awarded by the Advanced Research Projects Agency-Energy (ARPA-e) of the U.S. Department of Energy. The government has certain rights in the invention.