Unconventional carrier-mediated ferromagnetism above room temperature in   ion-implanted (Ga, Mn)P:C
  Ion implantation of Mn ions into hole-doped GaP has been used to induce ferromagnetic behavior above room temperature for optimized Mn concentrations near 3 at.%. The magnetism is suppressed when the Mn dose is increased or decreased away from the 3 at.% value, or when n-type GaP substrates are used. At low temperatures the saturated moment is on the order of one Bohr magneton, and the spin wave stiffness inferred from the Bloch-law T^3/2 dependence of the magnetization provides an estimate Tc = 385K of the Curie temperature that exceeds the experimental value, Tc = 270K. The presence of ferromagnetic clusters and hysteresis to temperatures of at least 330K is attributed to disorder and proximity to a metal-insulating transition. 
N. Theodoropoulou, A. F. Hebard, M.E. Overberg, C.R. Abernathy, S.J.   Pearton, S.N.G. Chu, and R.G. Wilson