Observation of L1[subscript]0-like chemical ordering in a decahedral FePt nanoparticle by C[subscript]s-corrected high resolution transmission electron microscopy

Abstract

The state of the chemical ordering in a decahedral FePt nanoparticle was studied using aberration corrected high resolution transmission electron microscopy. With the reduced image delocalization effect as a result of spherical aberration correction, it is possible to directly correlate the image intensity with the local state of chemical ordering through the help of a multislice image simulation. We have found direct evidence for the image intensity oscillation from one atomic layer to another. It is interpreted as L10-like chemical ordering, i.e., the alternate occupation of Fe and Pt atoms in the (002) planes. The result suggests that chemical ordering survives even in decahedral nanoparticles down to 3 nm size despite the possible surface effects.