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发帖数: 149 | 1 http://pubs.acs.org/doi/abs/10.1021/ja2005708
Three-dimensional colloidal crystals made of
ferromagnetic particles, such as magnetite (Fe3O4), cannot
be synthesized in principle because of the strong attractive
magnetic interaction. However, we discovered colloidal
crystals composed of polyhedral magnetite nanocrystallites
of uniform size in the range of a few hundred nanometers in
the Tagish Lake meteorite. Those colloidal crystals were
formed 4.6 billion years ago and thus are much older than
natural colloidal crystals on earth, such as opals, which
formed about 100 million years ago.1 We found that the
size of each individual magnetite particle determines its
morphology, which in turn plays an important role in
deciding the packing structure of the colloidal crystals. We
also hypothesize that each particle has a flux-closed magnetic
domain structure, which reduces the interparticle
magnetic force significantly. |
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