Rensselaer Researchers Create Tiny Magnetic Diamonds On The Nanoscale

In a paper published in the Aug. 26 issue of Physical ReviewLetters, the researchers report a technique to make magnetic diamondparticles only 4-5 nanometers across. The tiny diamond magnets couldfind use in fields ranging from medicine to information technology.

Ferromagnetism has been historically reserved for metals, butscientists are becoming increasingly interested in the prospect ofcreating metal-free magnets, particularly from carbon-based materials.Diamond is a naturally occurring crystalline form of carbon.

Magnets made from carbon could have a number of advantages overtheir metal counterparts. "Carbon is lightweight, very stable, simpleto process, and less expensive to produce," says Saikat Talapatra, apost-doctoral research associate with the Rensselaer NanotechnologyCenter at Rensselaer Polytechnic Institute.

Talapatra is lead author of the study, which also includedresearchers from NASA Ames Research Center in California; Richmond,Va.-based Philip Morris USA; and the University at Albany.

"These findings could lead to a systematic, controllable methodfor producing magnetic carbon materials," says Pulickel Ajayan, theHenry Burlage Professor of Materials Science and Engineering atRensselaer and co-author of the paper. "Though the value of themagnetization is much lower than in regular magnets, the nature of thespin interactions in carbon could lead to a number of potentialapplications."

Magnetic nanocarbons could make promising structures forhigh-density memory devices and in quantum computers. And becausecarbon materials are generally compatible with living tissue, thesenanostructures could be useful in medical applications such as magneticresonance imaging (MRI) and the targeted delivery of drugs to specificparts of the body.

Researchers have long known that defects and irregularities inpure carbon materials can give rise to electrons that are not pairedwith other electrons. Each "unpaired" electron produces a magneticfield by its spinning, and when all of the spins align, the materialitself becomes magnetic. Talapatra and his colleagues have developed away to modify the structure of carbon in a controlled manner by firingclusters of atoms at the diamond particles. This produces magnetism atroom temperature, and the total strength of the magnetism depends onthe amount and type of atoms used.

The next step, according to Talapatra, is to calculate how thetypes of defects and their concentration in the pure carbon structureaffect the magnitude of magnetism. "We are also working towarddeveloping simpler ways to make magnetic nanocarbons in a morecontrolled fashion," he says. "The long-term goal is to show some realapplications using these structures."

Other Rensselaer researchers involved in the work were RobertVajtai, laboratory manager for the Rensselaer Nanotechnology Center;Ganapathiraman Ramanath, associate professor of materials science andengineering; Mutsuhiro Shima, assistant professor of materials scienceand engineering; Gopal Ganesan Pethuraja, research engineer with theCenter for Integrated Electronics; and Taegyun Kim, graduate student inmaterials science and engineering.

The research was funded by NASA, Philip Morris USA, and the National Science Foundation.

Nanotechnology at Rensselaer
In September 2001, theNational Science Foundation selected Rensselaer as one of the sixoriginal sites nationwide for a new Nanoscale Science and EngineeringCenter (NSEC). As part of the U.S. National Nanotechnology Initiative,the program is housed within the Rensselaer Nanotechnology Center andforms a partnership between Rensselaer, the University of Illinois atUrbana-Champaign, and Los Alamos National Laboratory. The mission ofRensselaer's Center for Directed Assembly of Nanostructures is tointegrate research, education, and technology dissemination, and toserve as a national resource for fundamental knowledge and applicationsin directed assembly of nanostructures. The five other original NSECsare located at Harvard University, Columbia University, CornellUniversity, Northwestern University, and Rice University.

About Rensselaer
Rensselaer Polytechnic Institute,founded in 1824, is the nation's oldest technological university. Theuniversity offers bachelor's, master's, and doctoral degrees inengineering, the sciences, information technology, architecture,management, and the humanities and social sciences. Institute programsserve undergraduates, graduate students, and working professionalsaround the world. Rensselaer faculty are known for pre-eminence inresearch conducted in a wide range of fields, with particular emphasisin biotechnology, nanotechnology, information technology, and the mediaarts and technology. The Institute is well known for its success in thetransfer of technology from the laboratory to the marketplace so thatnew discoveries and inventions benefit human life, protect theenvironment, and strengthen economic development.