In this study, cubic and spherical FePt clusters were created by inert gas condensation in an argon-helium dc sputter discharge under different flow and target power conditions. The plasma recipes for spherical and cubic clusters called for high He:Ar ratio, low target power and low He:Ar ratio, high target power, respectively. As expected, Langmuir probe measurements show the recipes led to larger ion density for the cubic case (2 × 108 cm−3 versus 6 × 106 cm−3 for spherical). We conclude that the larger density of argon ions increased the cluster-ion collision probability, heating the clusters in situ to promote atomic rearrangements and the formation of the ordered L10 crystal structure rather than the disordered fcc structure.
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