Carbon, FePt enhance device storage performance
Led by Zhanhong Cen, a team of researchers at A*STAR Data Storage Institute in Singapore has revealed that, in addition to its magnetic characteristics, the optical response of FePt nanocrystals is suitable for high-performance data-storage applications. Furthermore, the use of laser light pulses improves the magnetic recording process.
"Decreasing the size of magnetic particles makes the magnetic information become thermally unstable due to an effect called superparamagnetism," explained Cen. "FePt nanoparticles are very promising, because for these nanoparticles, superparamagnetism is suppressed at room temperature."
But as determined in the research, FePt nanoparticles have a drawback: the magnetic field required for writing data is much higher than that produced by present disc drives. While the magnetic-field intensity necessary for a change of state could potentially be reduced by locally heating the material with a pulse of light, a process called heat-assisted magnetic recording, it is said that little was known about the optical response of FePt until today.
The researchers created thin-film samples using a process known as sputtering, which involves firing a beam of particles at a FePt alloy to release iron and platinum atoms. The atoms land on a glass substrate covered with a layer of magnesium oxide where they form crystals. Carbon was sputtered at the same time to form a single layer of FePt nanocrystals, 15nm in diameter and 9.1nm tall, embedded in a film of carbon.
For comparison, the team also created a nanocrystal sample without carbon and probed the refractive index and absorption of the two samples with both visible and near-infrared light. The researchers used these values in a computer model to simulate the performance of the material in a heat-assisted magnetic recording device. The sample doped with carbon came out on top.
"Our simulations show that introducing carbon into a FePt nanocomposite can improve optical performance," said Cen. "Ultimately, a FePt–carbon recording medium will perform better than current storage options, because it will use a smaller optical spot on the recording media and enable more energy-efficient writing and reading of data."