Voids adjacent to both cubic (ZnS-type) and hexagonal (NiAs-type) Mn-rich
nanocrystals are characterized using aberration-corrected transmission electron
microscopy in annealed Ga0.995Mn0.005As magnetic semiconductor specimen grown
by molecular beam epitaxy. Nano-beam electron diffraction measurements suggest
that the nanocrystals exhibit deviations in lattice parameter from that of bulk
MnAs. In situ annealing inside the electron microscope is used to study the
nucleation, coalescence, and grain growth of individual nanocrystals. After
annealing at 903 K, the magnetic transition temperature of the specimen likely
to be dominated by the presence of cubic ferromagnetic nanocrystals