K. Ouchi

Noise source and noise spectrum of perpendicular recording media

Abstract A noise source model based on small reversed domain structure was proposed for perpendicular recording media. The model indicates that a higher SQ⊥ along with a smaller reversed domain size is effective in reducing the medium noise, and the intrinsic medium noise spectrum has a white noise property. The intrinsic noise spectrum obtained by the experiment for Co–Cr-based perpendicular recording media exhibited a white noise property agreeing with the model. While the medium noise for a longitudinal recording medium exhibited a colored spectrum with a broad peak at a low frequency. The white noise property indicates high recording resolution property of the perpendicular recording media.

A new fabrication method for submicron trackwidth thin film heads

A new head structure suitable for submicron trackwidth writer and its fabrication method were described. The key features of the new head were to use the film thickness instead of the stripe width of the head core to define the recording trackwidth and a laminated dual-axis anisotropy back-core to improve the flux carrying efficiency in the head. The front gap of the head was fabricated by focused ion beam precision machining/deposition. A wall angle of 1° was achievable for a gap milled in a 1 μm-thick track-core. The dual-axis film, which consists of two uniaxial sandwiches with their easy axes orthogonally oriented, exhibited isotropic BH loops and isotropic high-frequency permeability after RFA. Significant improvement of magnetisation response and flux conduction of the dual-axis core after RFA were observed by SKEM examinations with the cores excited by an electromagnet at frequency of 0.5 MHz and by a single-turn coil at 10 MHz. Although the dual-axis film exhibited isotropic magnetic properties after RFA, SKEM observations indicate that the two uniaxial sandwiches in the dual-axis core behaved independently. The isotropic magnetic properties of the dual-axis films after RFA appear to be the average effect of the two uniaxial sandwiches. The high frequency flux conduction was more effective along the hard axis than along the easy axis. The effective flux conduction in the dual-axis core was attributed to the contribution of hard axis behaviour of each uniaxial sandwich. However, domain wall motion-type response was also observed in the dual-axis core.

Pt and Pd intermediate layers for controlling Co-Cr-Nb-Pt layer growth in double layered perpendicular magnetic recording media

The role of intermediate layers in double layered perpendicular media is discussed. A newly proposed Pt/Ti layer can control the storage layer crystallite to be fine and uniform. Magnetic property was then improved to show high coercivity and squareness normal to the film in the very thin thickness region. It was found that reduction in the initial growing layer thickness of the storage layer was achieved by suppressing oxygen diffusion.

Detection of extremely high bit density signals with a narrow track width GMR head in double layered perpendicular recording media

Abstract Recording resolution, medium noise and thermal stability have been investigated for double layered perpendicular magnetic recording media. The recording performance was improved by introducing a stacked intermediate layer between a soft magnetic backlayer and a storage layer due to increased crystal orientation with a small magnetic domain size and suppressed initial growing layer of the storage layer. The reproduced output at an extremely high linear density of 950xa0kFRPI was detected by using a contact-type CF-SPT head for write and a GMR head with a narrow read track width of 0.4xa0μm.

Preparation of CoCr films for perpendicular recording by sputter deposition at extremely high Ar pressures

Abstract High Ar pressure sputtering which enabled the deposition of Coue5f8Cr films with high coercivity at room temperature, has been extended to high substrate temperature deposition. Coue5f8Cr films deposited at a high temperature of 250°C exhibit higher perpendicular coercivity and larger perpendicular anisotropy than those of room-temperature deposited films due to a magnetically isolated columnar structure. The origin of the magnetic isolation of grains can be explained by Cr micro-segregation not within grains but at the grain boundaries.