This paper presents a method to investigate the characteristics of hydrodynamic bearings of a HDD spindle motor considering the variation of the clearance as well as the lubricant viscosity due to elevated temperature. Iterative finite element analysis of heat conduction and thermal deformation is performed to determine the viscosity and clearance of hydrodynamic bearings at elevated temperature until the temperature in the bearing area converges. The proposed method is verified by comparing the calculated temperature with the measured one at elevated surrounding temperature as well as in room temperature. This research shows that elevated temperature changes the clearance as well as the lubricant viscosity of the hydrodynamic bearings of a HDD spindle motor. Once the viscosity and clearance of hydrodynamic bearings of a HDD spindle motor are determined, finite element analysis of the Reynolds equation is performed to investigate the static and dynamic characteristics of hydrodynamic bearings of a HDD spindle motor at elevated temperature. It also shows that the variation of clearance due to elevated temperature is another important design consideration which affects the static and dynamic characteristics of the hydrodynamic bearings of a HDD spindle motor.

Thermal stability of the present CoCrPt–SiO2 media becomes a more critical issue as recording density steadily increases. In the present study, thermal stability of the stacked media composed of high Ku CoPt–TiO2 and normal Ku CoCrPt–SiO2 was studied by changing stacking order and thickness of each layer while keeping a constant total thickness. When the CoPt–TiO2 layer was placed under the CoCrPt–SiO2 layer, negative nucleation field and coercivity increased much more than those of the reverse stacking case. Thermal stability of the CoPt–TiO2 bottom group was superior to that of the CoCrPt–SiO2 bottom group when measured by a spin stand.

PACS 75.50. Ss, 85.70.Li In this study, we introduced the new concept SUL (Soft Underlayer) of PMR (Perpendicular Magnetic Recording) media for the superior recording performance. The recording performance of PMR media with various SUL types were investigated by Guzik spin stand. Our new concept SUL, which was denoted by the modified SAF (Synthetic Antiferromagnetic Coupling) structure, showed more excellent recording properties than those of others. These improved recording performances may be generated by decreased SUL noise and increased filed gradient with new SUL structure. The obtained results indicated that the modified SAF SUL structure can be helpful to high recording density.

This research investigates hew the design variables of ball bearing change the beating stifthess 'and the natural frequencies of a HDD spindle system in elevated ternperature. It shovis that large contact angle reduces the variation of the bearing stiffhess and the natural frequencies in elevated terrrperature. It also proposes a robust design of the spindle motor, in which the wave spring maintains the constant preload even in elevated temperature. The theoretical investigation shews that the reduction ofnatural frequencies due to temperature rise is almos! negligible in the proposed HDD spindle system,

No abstract