Observations of nanocrystals in thin TbFeCo films

Observations of thin films of amorphous TbFeCo by electron microscopy with a resolution limit of better than 0.2 nm invariably reveal the presence of very fine microcrystals (sizes ∼2-5 nm). Bright field imaging, in both plan view and in cross section, indicates that these nanocrystals have the crystal structure of α-Fe or Co. In contrast, crystals of Tb metal (or Tb oxides) have not been observed. Similar observations of FeCo thin films, prepared under identical experimental conditions, reveal much larger crystals (typically 10-50 nm). It is concluded that the presence of the rare earth element Tb is crucial to the microstructure displayed by this kind of material.