  We report the annealing-induced enhancement of ferromagnetism and
nano-particle formation in group-IV-based ferromagnetic-semiconductor GeFe. We
successfully increase the Curie temperature of the Ge0.895Fe0.105 film up to
~220 K while keeping a single ferromagnetic phase when the annealing
temperature is lower than 500{\deg}C. In contrast, when annealed at 600{\deg}C,
single-crystal GeFe nano-particles with stacking faults and twins, which have a
high Curie temperature nearly up to room temperature, are formed in the film.
Our results show that annealing is quite effective to improve the magnetic
properties of GeFe for high-temperature-operating spin-injection devices based
on Si or Ge.
