Integrated Nanostructured Systems

TEM image of a self-assembled array of monodisperse Fe₃O₄ nanoparticles.

Magnetoresistance as a function of field for the Fe₃O₄ array; lines are fitting to the data.

Large, positive magnetoresistance for a Co nanoparticle array.

Synthesis and self-assembly of nanoparticles and nanowires; nanoscale magnetism; charge transport in self-assembled nanostructures; biological applications of nanoparticles.

Material synthesis: we are developing various bottom-up fabrication techniques for nanostructures. They include the chemical synthesis of nanoparticles, vapor phase growth of nanowires and templated growth of nanodot arrays with thin film techniques.

Magnetism in nanostructures: we have observed reduction and unusual temperature dependence of magnetization behavior in FePt nanoparticle systems. They were attributed to competing exchange interactions that contribute differently at the particle surface and interior. This is important in understanding the magnetic behavior of nanostructures and their applications.

Charge transport in nanostructures: We have investigated spin dependent charge transport in a number of magnetic nanoparticle systems including magnetite and Cobalt. Field dependence of magnetoresistance is found to be dominated by non-collinear spins at the nanoparticle surfaces.

Applications: we have developed highly ordered FePt nanodot arrays with large perpendicular anisotropy, high coercivity and extremely high density that may have potential applications in future magnetic data storage media; we are also interested in biological applications of magnetic and hybrid nanoparticles.

Physical Property Measurement System with Vibrating Sample Magnetometer option for magnetic and charge transport measurements.