My research focuses on magnetic nanoparticles that have very uniform sizes, and we study their fundamental behavior, as well as possible applications in data storage media, permanent magnets, and biomedicine. One of the consequences of this monodispersity is that the particles can then self-assemble into arrays (shown below), just as atoms come together to form a crystal. We are investigating the collective behavior of the nanoparticle arrays that are analogous to those in crystals. Isolated iron atoms do not interact with each other and are paramagnetic, but in an iron crystal the interactions lead to ferromagnetism. Superparamagnetic-to-ferromagnetic and insulator-to-metal phase transitions are expected as the nanoparticles are brought closer together. We have also developed a method to replace the surfactant coating the particles with an inorganic matrix, and are exploring methods that exploit this approach to prepare functional nanocomposites.

More details about current research projects, current group members, and financial support can be found at the Majetich group home page: http://www.andrew.cmu.edu/user/sm70

Selected Publications

Self-Assembled Nanoparticle Arrays as Nanomasks for Pattern Transfer, M. Sachan, C. Bonnoit, C. Hogg, E. Evarts, J. A. Bain, S. A. Majetich, J.-H. Park, and J. G. Zhu, J. Phys. D 41, 134001 (2008).

Field Evolution of Magnetic Correlation Lengths in e-Co Nanoparticle Assemblies, M. Sachan, C. Bonnoit, S. A. Majetich, Y. Ijiri, P. O. Mensah-Bonsu, J. A. Borchers, and J. J. Rhyne, Appl. Phys. Lett. 92, 152503 (2008).

Synthesis and Single Particle Optical Detection of Low Polydispersity Plamsonic Superparamagnetic Nanoparticles, J. K. Lim, R. D. Tilton, A. Eggeman, F. Lanni, and S. A. Majetich, Adv. Materials, 20, 1721 (2008).

Saturation of Nuclei Concentration in the Phase Transformation of FePt Nanoparticles, Y, Ding and S. A. Majetich, IEEE Trans. Mag. 43, 3100-3102 (2007).

Size and Concentration Effects on High Frequency Hysteresis of Iron Oxide Nanoparticles, A. Eggemann, S. A. Majetich, D. F. Farrell, and A. Q. Pankhurst, IEEE Trans. Mag. 43, 2451-2453 (2007).

Design and Synthesis of Plasmonic Magnetic Nanoparticles, J.-K. Lim, R. Tilton, A. Eggeman, and S. A. Majetich, J. Magn. Magn. Mater. 311, 78-83 (2007).