A. Itoh

Near-field optically assisted hybrid head for self-aligned plasmon spot with magnetic field

Magneto-optical hybrid head is one of the key devices for the optically assisted magnetic recording. However, there has not been enough research about the hybrid head. Here, we present a near-field optical advanced hybrid (NOAH) head, which makes a self-aligned plasmon spot with a magnetic field. Since a near-field optical intensity distribution is strongly affected by the presence of the recording medium, the shape of the electrode is analyzed by a finite difference time domain method with the TbFeCo film as the recording medium. We calculate the dependences both for the optical and magnetic characteristics on a gap distance between the electrode and the recording medium. The NOAH head makes the sharp distribution of light intensity (full width at half maximum ∼40nm) with the magnetic field ∼29Oe∕mA in the case for 5nm in gap distance. We also calculate the dependence of the plasmon effect on electrode materials. It is revealed that the material which has a high extinction coefficient shows a high peak i...

Finite difference time domain simulation on near-field optics for granular recording media in hybrid recording

We demonstrate the near-field optics on granular recording media calculated by finite difference time domain (FDTD). Granular media and pattern media are necessary for hybrid recording to achieve a recording density of 1Tbit∕in.2. In FDTD simulation, the power of near-field optics from a plasmon antenna is affected by the presence of the medium. However, for further investigation, the model of this study included granular media. The grains are arrayed in a close-packed structure. From this analysis, the top of the grains shows strong power of near-field optics. The power intensity of the granular media under the apex of the plasmon antenna shows a narrow distribution with a sharp peak, about three times higher than that for film media. There are higher peaks in intensity at the surface of the grain than inside the grain. These results show that grains positioned at the apex of the antenna can be heated by a small, concentrated spot.

Excitation of coherent spin waves at ultrafast thermomagnetic writing

We present results of a time-resolved study of the ultrafast magnetic response of Gd/sub 23.1/Fe/sub 71.9/Co/sub 5.0/ magnetically amplified magnetooptical systems (MAMMOS) structures under conditions near actual read/write temperatures. 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 magnetooptical Kerr effect. Our experiment clearly demonstrates that the photo-excitation effectively excites coherent spin waves in the magnetic material. Precession frequencies of several gigahertz and relaxation times in the nanosecond range were observed.