As quick as light: All-Optical Magnetic Data Storage World fastest magnetic reversal by light

Observation and Control of Ultrafast Dynamics of Spins by Femto Second Pulse Laser
Dept. of Electronics & Computer Science
Assistant Professor Arata Tsukamoto

The ever increasing the capacity of storing information motivates the search for faster approaches to process and magnetically record information. Most computers store data on magnetic hard disk drives, in which the direction - “up” or “down” - of the magnetic moments in a small region of the disk corresponds to a binary bit. However, it was faced to unavoidable fundamental problem for faster operation in conventional way.
We have experimentally demonstrated controlled magnetization reversal induced by a single 40 femtosecond (40 x 10-15s) circularly polarized laser pulse in the magnetic GdFeCo thin film, a material relevant for data storage. No external magnetic field is required for this opto-magnetic switching, and the stable final state of the magnetization is unambiguously determined by the helicity of the laser pulse (see the Figure 1). This finding, previously believed to be fundamentally impossible, reveals an ultrafast and efficient pathway for writing magnetic bits at 100000 times faster speeds compared with the conventional Hard Disk Drive.
Our result (Physical Review Letters (Vol. 99, 047601-(pp. 1-4) (2007))) got much attention across the world as might have a strong impact on the future of the data storage technology. (e. g. Nature Photonics 1, 494 (2007),ScienceNOW, 28 June (2007), Physics News Update, 830 #1, June 27, (2007), etc. ) Again, the ever increasing technological importance of spintronic devices, which exploit the spin of the electron, as well as the push to integrate the element, motivates the search for faster approaches to manipulate spins. Our study was received to scientific research program PRESTO(Precursory Research for Embryonic Science and Technology) of Japan Science and Technology Agency as involving fundamental important matter for constructing next generation spintronic devices.
In our research, an all-optical pump and probe method was used in which an intense (pump) light beam excited a medium due to ultrafast laser heating and a less intense (probe) beam monitored this photo-excited state through the magneto-optical Kerr effect with femtosecond time resolution. Based on these new discoveries, we are striving to establish the fundamental techniques of researching and developing ultrafast spin manipulation.