Shintaro Miyanishi

High-density laser-assisted magnetic recording on TbFeCo media with an Al underlayer

The effects of an Al underlayer with a nanoscaled rugged structure are studied on the laser-assisted magnetic recording of TbFeCo media. The performance of laser-assisted recording is dramatically improved by employing the Al underlayer. The reproducing signal is observed at the linear density of 450 kilo-flux change per inch. The relationship between the surface morphology and the magnetic properties of TbFeCo media proves that the nanoscaled rugged structure of Al underlayers influences the process of the magnetization reversal; in particular, the coercivity and the exchange interaction are significantly changed in the TbFeCo media. The authors conclude that the nanoscaled rugged structure of the Al underlayer leads to magnetic pinning sites, which impede the motion of a magnetic domain wall, and thereby the laser-assisted recording performance is improved.

Effect of underlayers of laser-assisted magnetic recording media on high-density recording

The effect of underlayers of laser-assisted magnetic recording media has been investigated from the view point of high-density magnetic recording. The frequency response of a carrier-to-noise ratio (C/N) was measured in the media with various kinds of underlayers. It was found that they affect the high-frequency recording capability; the C/N at higher frequencies has been drastically improved for an Al-underlayered recording medium and a C/N of 40 dB was obtained at a recording frequency of 45 MHz and a track width of 0.35 μm. These results are explained by the surface morphology of the underlayer and its pinning effect on the domain-wall motion that is considered to work well for recording smaller stable domains.

Monolithically Fabricated Hybrid Head for Near-Field Assisted Magnetic Recording

In this paper, we show a monolithically fabricated hybrid head with a GaAs-based laser diode capable of near-field-assisted magnetic recording. A bottlenecked conductor was placed beside the laser cavity formed on the trailing side of the head. The bottlenecked structure is used as a generator of magnetic and near fields. The structure consists of a couple of opposite electrodes with a 200-nm gap and a bridge connection between the electrodes. The magnetic field is mainly generated around the bottleneck by feeding current through the conductor. The near field is produced along edges of the bottleneck by irradiating a laser beam. We confirmed the 3-D localization of near field in the nanometer size around the bottleneck by means of a near-field scanning optical microscope. We attained the nanosized overlap between magnetic filed and near-field distributions on the hybrid head with the laser diode.

SNOM Observations of Surface Plasmon Polaritons on Metal Heterostructures

We observe surface plasmon polariton (SPP) refraction on a metal heterostructured sample with a scattered-type scanning near-field optical microscope (SNOM). The sample consists of Al and Au in-plane whose boundary is smooth enough with proper etching time. SPPs excited on the Al film travel to the boundary and a portion of SPPs propagates into the Au film. In addition, interference fringes appear in the SNOM image bent at the boundary. The result is analysed with effective index method and the refracted angle is explained by Snells law.

Huge magnetoresistive effects using space charge limited current in ZnO/SiO2 system

Huge magnetoresistive effects were observed in a metal/insulator current-in-plane (CIP) diode feeding space charge limited (SCL) current. The insulator laterally toward opposite gold (Au) electrodes was fabricated on a SiO2 substrate by the standard photolithography method using dry etching. The insulator consisted of a SiO2∕ZnO∕SiO2∕ZnO multilayer sputtered on the substrate. Current-voltage curves showed Ohmic property and SCL current characteristics accompanied by Child-Langmuir and Mott-Gurney laws derived from first order differential calculus. Current-magnetic field curves indicated the huge magnetoresistive effects up to 1010% under the magnetic field of 0.3T at room temperature. The current-magnetic field curves have even symmetry for the applied magnetic field. The Au/insulator CIP diode is abruptly switched between a conducting state and an insulating state by the applied magnetic field.

High Density Recording Capability of Laser-Assisted Magnetic Recording

Laser-assisted magnetic recording technology enables narrower track recording than the track width of a magnetic head. This paper considered a linear recording density for the laser-assisted magnetic recording by comparing the performance of laser-assisted magnetic recording with that of non-assisted magnetic recording. The result shows that the laser-assisted magnetic recording has the ability of narrow track formation without loss in frequency response.