Research is closing in on the next-generation of ultra-high-density magneto-optical storage devices that could store more than 6,000 Terabits (6 petabits) of data, more than 70 times the contents of the entire U.S. Library of Congress, on a single 5-inch disc. Yet the vast storage amount is limited by the ability to write data quickly enough to the device. In the Journal of Applied Physics, researchers at Sun Yat-Sen University in China have demonstrated a way to record on ferromagnetic films using a laser-assisted ultrafast magnetization reversal dynamics.
The technique uses so-called time-resolved polar Kerr spectroscopy combined with an alternating magnetic field strong enough to re-initialize the magnetization state of gadolinium-iron-cobalt (GdFeCo) thin films. Tianshu Lai and colleagues showed that the magnetization reversal could occur in a sub-nanosecond time scale, which implies that next- generation magneto-optical storage devices can not only realize higher recording densities but also ultrafast data writing of up to a gigahertz. Such speed is at least thirty times faster than that of present hard disks in computers.
Laser-assisted magnetic recording was demonstrated on a sub-picosecond time scale under a saturated external magnetic field. "We found that the rate of magnetization reversal is proportional to the external magnetic field," says Lai, "and the genuine thermo-magnetic recording should happen within several tens to hundreds of picoseconds when we apply a smaller magnetic field than the coercivity of the recording films."
- Zhifeng Chen, Ruixin Gao, Zixin Wang, Chudong Xu, Daxin Chen, Tianshu Lai. Field-dependent ultrafast dynamics and mechanism of magnetization reversal across ferrimagnetic compensation points in GdFeCo amorphous alloy films. Journal of Applied Physics, 2010; 108 (2): 023902 DOI: 10.1063/1.3462429
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