11-10
J. Nozawa, K. Tsukamoto, W. Van Enckevort, T. Nakamura, H. Miura, H. Satoh,
K. Nagashima, M. Konoto,
Magnetite 3D colloidal crystals formed in the early solar
system 4.6 billion years ago,
J. Am. Chem. Soc. 133 (2011) 8782-8785
Abstract
Three-dimensional colloidal crystals made of ferromagnetic particles,
such as magnetite (Fe(3)O(4)), 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.