A Co/Cu solid solution is prepared by direct implantation of 200 keV Co+ io
ns into Cu targets. The maximum concentration at this ion energy is limited
to 25 at% Co due to sputtering. Magnetic measurements show a spin-glass be
haviour, as expected for a solid solution of Co in Cu. At about 630 K the s
olid solution starts to decompose into clusters. After heat treatment, ferr
o- and superparamagnetic behaviour is observed, indicating that the size of
the clusters is broadly distributed. (C) 1999 Elsevier Science B.V. All ri
ghts reserved.