Effects of Head Pole Aspect Ratio and Skew Angle on Areal Density in Perpendicular Recording

Abstract

Semianalytical models have been applied to examine the effect of head pole aspect ratio on areal density in perpendicular recording at different skew angles. It has been found that at zero skew angle, increasing pole length enhances the writing field, which allows higher medium and smaller grain size and leads to higher areal density. However, when the skew angle is included, the pole aspect ratio needs to be optimized to deliver the optimal areal density. Both the optimal areal density and pole aspect ratio decrease with increasing the skew angle.

Mechanisms of Minimum Skew Angle Actuation for Hard Disk Drives

“…The guider track profile (x, y) can be determined by (3) and (4). An implementation of the guider track actuation mechanism in a hard disk drive is shown in Figure 5.…”

“…Based on the analysis of head pole aspect ratio and skew angle effects on areal density in perpendicular recording [4], the benefits of small skew gain on areal density for a slant suspension assembly and the guider track actuator assembly are compared and the issues are discussed as shown in Table 1. For the slant suspension assembly, the actuator arm length is to be increased by about 30% of the original design, resulting in the in-plane first resonance frequency dropping by 20 to 30%, leading to degraded control bandwidth and shock resistance.…”

“…The remedies include reducing the actuator inertia, specifying the proper suspension to arm length ratio, and designing high bandwidth VCM arm and suspension structures [1], and so on. In addition, introducing a secondary stage actuator for dual stage control of the head element is an 02002-p. 4 effective way to increase the actuator servo bandwidth [11,12]. Furthermore, reducing vibration due to air flow, spindle motor, disk, etc., can relax the requirements on servo bandwidth [13.]…”

“…The track density and areal density can be increased more than 20% when the skew is 0° compared to that of 15° skew. Previously IBM proposed a parallel flexural in-line actuator for magnetic recording disk drives which has a small skew angle of 1.5q [4]. However, this design makes a significant change in the actuator structure compared to current actuator designs.…”

High-density perpendicular recording—advances, issues, and extensibility

“…11, from Ref. [6] illustrates the impact of skew on areal density for a head with W pole =50 nm, Flare=20 nm, d=15 nm. H k and D grain were adjusted to accommodate the write field variations related to pole length while keeping constant thermal stability, impacting BPI as well as TPI.…”