Observation of the Ordered CoPt3 Alloy in Co-Pt Multilayers

Abstract
We report results of a synchrotron X-ray diffraction study of Co-Pt multilayers, with Pt[111] as the growth axis. The multilayers were grown by MBE on Pt seedfilms on basal-plane sapphire substrates at growth temperatures of 100 and 200ºC.The multilayers comprised 15 periods of Co 3Å, Pt 15Å and both exhibited perpendicular anisotropy. Grazing-incidence radial- and phi-scans revealed a set of {110{ peaks indicating doubling of real space periodicity consistent with the presence of the ordered alloy CoPt3. This supports the results of other studies which indicate interdiffused interfaces in Co-Pt multilayers and shows that chemical ordering can occur at much lower temperatures than in bulk alloys where annealing times of several days at ∼ 700ºC are required to stimulate ordering.