Tailoring magnetic nanocrystal superlattices by chemical engineering

Recognizing the technological potential of magnetic nanocrystals for the next generation of high density data storage [S. Sun and C. B. Murray, J. Appl. Phys. 85, 4325 (1999)] and as markers in biological systems for detection and manipulation of attached molecules, [L. Lagae, R. Wirix-Speetjens, J. Das, D. Graham, H. Ferreira, P. P. F. Freitas, G. Borghs, and J. De Boeck, J. Appl. Phys. 91, 7445 (2002)] ligand stabilized nanoparticles prepared via high-temperature solution-phase synthesis [C. B. Murray, S. Sun, W. Gaschler, H. Doyle, T. A. Betley, and C. R. Kagan, IBM J. Res. Dev. 45, 47 (2001); V. F. Puntes, K. M. Krishnan, and A. P. Alivisatos, Science 291, 2115 (2001)] rapidly gain interest in research and development. Following a chemical preparation route recently proposed [V. F. Puntes, K. M. Krishnan, and A. P. Alivisatos, Science 291, 2115 (2001)] Co and FeCo alloyed nanocrystals have been synthesized with different nanocrystal size distributions employing different growth rates during preparation. The resulting magnetic properties are a function of the particle size distribution and can be tailored for superparamagnetic or ferromagnetic behavior at room temperature. In addition, the possibility of synthesizing FeCo alloyed nanoparticles is demonstrated and discussed. (C) 2003 American Institute of Physics.