Magnetic Nano-Particles, Nanocomposites, and Films

Brief Description
Brief Description:
This is a method for producing nanometer-sized magnetic composite particles, bulk materials, and granular films of hard (high coercivity) magnetic materials of iron-platinum alloy. 

The process can produce the face-centered tetragonal (fct) form of FePt, which is particularly desirable because of its high magnetic anisotropy, high coercivity and small domain wall width (about 3 nm), minimal stable grain sizes (about 2.9 to 3.4 nm) and chemical stability.   The synthesis process includes the creation of platinum-maghemite (Pt core and maghemite shell) nanoparticles, which serve as precursors for magnetic FePt nanoparticles and nanocomposites. These particles may also have potential applications for catalysis.  Similar synthesis processes are being used to create composite materials of Co cores in iron oxide shells, SmCo cores in iron oxide shells.
FePt nanoparticles have been recognized to have potential use in data storage at area densities approaching 1 Tbit per square inch.  (Current hard drives are at about 100 Gb per squarer inch.) Many research groups in universities and in industry (IBM, Seagate, Hitachi, Fuji Electric, etc.) are studying methods for fabricating and assembling face-centered tetragonal FePt nanoparticles. Currently monodisperse magnetic nanoparticles of FePt are synthesized through the simultaneous reduction of metal salts and or thermal decomposition of organometallic compounds, which typically result in disordered face-centered cubic particles.  Our colloidal synthesis method produces particles in the preferred fct phase, and in a size range, from about 5 to 25 nm, appropriate for high coercivity.

The core-shell technique enables the construction of materials with a hard magnetic core in a soft magnetic matrix.  Such a composite enables a very high energy-product magnetic material, which could be useful in the fabrication of very high energy-product permanent magnets.  DARPA has an interest in such materials with high energy-product /low weight for applications in aircraft, automobile electric drive and propulsion, and efficient motor components.
This characteristic of having ferromagnetic particles embedded in an antimagnetic matrix helps to align the ferromagnetic moments and at the same time stabilize the magnetization.  This feature can be particularly valuable for making granular films for computer hard drives.   This is expected to be the most significant application area.
The advantage of this invention is expected to be a controlled fabrication process for this new class of composite magnetic nanoparticles and granular film.  The process can  produce the FePt alloy in the preferred fct form and in a size range appropriate for high coercivity.   The general synthesis process is being applied to a variety of related materials, with the ability to construct composites of widely varying magnetic properties.   The process can, for example, make nanoparticles of superparamagnetic CoFe. 
Patent Information:
Title Country Patent No. Issued Date
Core-Shell Magnetic Nanoparticles and Nanocomposite Materials Formed Therefrom United States 7,029,514 4/18/2006
For Information, Contact:
John FahnerVihtelic
Senior Licensing Manager
University of Rochester
Hong Yang
Xiaowei Teng