  Room-temperature ferromagnetism has been induced within ZnO single crystals
by implant-doping with Fe ions. For an implantation temperature of 620 K and an
ion fluence of 4x10^16 cm^-2, very tiny Fe particles, formed inside the host
matrix, are responsible for the ferromagnetic properties. They were identified
using synchrotron X-ray diffraction and Moessbauer spectroscopy. On the other
hand, Fe ions implanted at a temperature of 253 K and an ion fluence of 4x10^15
cm^-2 are incorporated into the host matrix and develop a room temperature
diluted magnetic semiconductor (DMS).
