FePt and CoPt Nanoclusters

For free-clusters, the cluster size distribution can be measured by the time-of-flight mass spectrometer for cluster films deposited on substrate by the cluster beam, the measurement of size distribution and observation of nanostructure are mostly done using transmission electron microscopy (TEM). In this section we will focus on the latter and pay special attention to FePt, CoPt clusters which have high anisotropy Tl0 phase after annealing [43-45]. For the TEM observations, FePt, CoPt nanoclusters, produced in a gas-aggregation chamber, in which high pressure Ar gas ( 0.5-lTorr) was applied and cooled by LN2, were directly deposited onto carbon-coated films supported by Cu grids. 

Similar results were also obtained for CoPt nanoclusters and shown in Fig. 12 is the high resolution TEM image for CoPt clusters with average size of 4.9 nm (cr= 0.46 nm, dd= 0.09), prepared with sputtering power of 160 W. 

FePt C nanocluster films were prepared with a multilayer method in which FePt cluster layers and C layers were alternately deposited onto a Si substrate. C served to isolate the clusters and to avoid cluster-aggregation during thermal annealing. The average FePt cluster size is about 4.5 nm. The nominal thickness of each cluster layer is about 1 nm, so that the FePt clusters can be well separated with C layer. The thickness of C layer was adjusted with C volume fraction changing from 7 to 45 % [48], 

Dynamics of Magnetization Reversal in FePt C Cluster Films 

Dilute FePt C Cluster Film Stoner-Wohlfarth-Like Behavior 

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