Abstract
Cobalt ions with the energy of 380 keV were implanted in pure copper. Changes in magnetic properties and local atomic structure around cobalt atoms which were induced by the implantation and the subsequent annealing at 873 K were investigated by using the SQUID and XAFS measurements, respectively. Just after the implantation, cobalt atoms replaced the regular copper atom sites in copper-fcc structure, and the magnetic state of cobalt atoms was nearly the paramagnetic state. By the subsequent annealing at 873 K for 1 hour, cobalt clusters which had the hexagonal close-pack (hcp) structure were produced, and the superparamagnetic state appeared. By the annealing for 24 hours, as each cobalt cluster grew to a larger size, and magnetic domain structures were produced in each cobalt cluster, the ferromagnetic state appeared.
