Reentrant magnetic behavior in fcc Co-Cu alloys

Crystalline ${\mathrm{Co}}_{\mathit{x}}$ ${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$ alloys, which cannot be obtained by equilibrium methods, have been fabricated by magnetron sputtering. The magnetic properties of the alloys, whose structure remains single-phase fcc up to x=0.80, is studied over the entire range of compositions. As in the case of other random magnetic systems such as Fe-Au, the metastable alloy is seen to evolve from a spin glass at low Co concentrations to a reentrant spin glass with evidence for both ferromagnetic and spin-glass ordering, and finally to a ferromagnet for x>0.40. A magnetic phase diagram for fcc Co-Cu is proposed.