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Magnetic Irreversibility And The Verwey Transition In Nanocrystalline Bacterial Magnetite, Ruslan Prozorov, Tanya Prozorov, Surya K. Mallapragada, Balaji Narasimhan, Timothy J. Williams, Dennis A. Bazylinski Jan 2007

Magnetic Irreversibility And The Verwey Transition In Nanocrystalline Bacterial Magnetite, Ruslan Prozorov, Tanya Prozorov, Surya K. Mallapragada, Balaji Narasimhan, Timothy J. Williams, Dennis A. Bazylinski

Chemical and Biological Engineering Publications

The magnetic properties of biologically produced magnetite nanocrystals biomineralized by four different magnetotactic bacteria were compared to those of synthetic magnetite nanocrystals and large, high-quality single crystals. The magnetic feature at the Verwey temperature TV was clearly seen in all nanocrystals, although its sharpness depended on the shape of individual nanoparticles and whether or not the particles were arranged in magnetosome chains. The transition was broader in the individual superparamagnetic nanoparticles for which TB < TV, where TB is the superparamagnetic blocking temperature. For nanocrystals organized in chains, the effective blocking temperature TB > TV and the Verwey transition is sharply defined. No correlation between particle size and TV was found. Furthermore, measurements of M (H,T,time) suggest that ...