Tuesday, December 9, 2008

Nano-magnetic sensors could pave the way for massive data storage capacity

By Rick C. Hodgin
Tuesday, December 09, 2008 14:25

Troy (NY) - Researchers at Rensselaer Polytechnic Institute (RPI) have created nanoscopic magnetic sensors. Comprised of carbon nanotubes embedded with bundles of cobalt atoms, these magnetic field sensors are the first ever capable of reliably detecting magnetic fields at near atomic levels.

RPI is calling its discovery "a new class of magnetic materials." The nano-device's cobalt clusters are embedded within the walls of a multi-layered carbon nanotube, just 1 nm to 10 nm in diameter. Since the clusters are internal to the tubes, rather than external, "they do not cause electron scattering and thus do not seem to impact the attractive conductive properties of the host carbon nanotube," according to assistant professor Swastik Kar, Department of Physics, who led the project.

A series of experiments has shown that the cobalt-cluster carbon nanotubes are sensitive enough to detect even miniscule magnetic fields present at near-atomic levels. RPI believes this is the first time such small magnetic fields have been reliably detected using carbon nanotubes, and it provides a new tool for analyzing the nanoscopic magnetic properties of many everyday items - something that was not possible previously due to an interference of the source materials used in the detector.

Future applications

According to the research paper, potential future applications include "new generations of nanoscale conductance sensors, new advances in digital storage devices, spintronics, and selective drug delivery components." Today's most advanced perpendicular storage techniques allow up to around 200 Gb of data per square inch (25 Gigabytes). Hard drives on the order of 10 nm per bit would allow upwards of 10 Petabits (Pb) per square inch - though realistic applications would be closer to 100 Terabits per square inch. Perpendicular storage solutions are expected to max out around 1 Terabit per square inch, though this ceiling appears to be constantly moving.

Today, semiconductors companies often utilize infrared emissions to detect electron movement through silicon-based transistors. TG Daily had the opportunity to visit Intel's debug lab in Nov, 2007. The laser probes used in that lab detect the emission of infrared light, which is transparent to silicon, and seeps through the back of the chip while the CPU is running.

By monitoring photon activity on the chip with the laser probe, the CPU debuggers can isolate individual circuits in operation. This helps them detect errors for chip designers and track down other problems or inefficiencies. This new RPI device may also produce an alternate method for detecting this kind of circuit activity.

The results of this study were published in an article entitled "Detection of Nanoscale Magnetic Activity Using a Single Carbon Nanotube" in Nano Letters.


Funding for this project was provided by the New York State Interconnect Focus Center at Rensselaer. Additional authors on the Nano Letters paper include Caterina Soldano, a postdoctoral research assistant at the Centre d’Elaboration de Matériaux et d’Etudes Structurales in Tolouse, France. Also, Professor Saikat Talapatra of the Physics Department of Southern Illinois University-Carbondale. And Professor P.M. Ajayan of Rice University's Department of Mechanical Engineering and Materials Science.

Other research

Additional recent carbon nanotube-related research from RPI includes a nanoscopic pressure sensor made of carbon nanotubes. RPI has also recently developed a solar cell coating which allows panels to absorb 90% of sunlight without the need for servos which track the sun's movement across the sky.