Dynamically clearance control by transient interface voltage with less modulation
Publication Date: 2014-Feb-17
The IP.com Prior Art Database
Disclosed is a device to dynamically control reader/writer clearance in a hard drive by transient interface voltage achieving less modulation, even for a head assistant magnetic recording hard disk drive.
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Heat-assisted magnetic recording (HAMR) is an potential technology in hard disk drive to take high-stability magnetic compounds without superparamagnetic effect, where magnetically records (writes) data using laser thermal assistance to first heat the material, as shown in Fig.1. Where the laser of light delivery (LD) can induce a heat protrusion, which can cause the transient reader/writer clearance change. Therefore, it is necessary to develop a new technology to control or compensate the clearance change from reading to writing for HAMR.
Fig.1 Illustration of heat-assisted magnetic recording technology
Thermally fly height control (TFC) is a clearance control technology in a hard disk drive. For non-HAMR drive, TFC heater power is adjusted while the head is from reading to writing with inducing writer current Iw which can cause writer protrusion with a writer clearance change, shown in Fig.2. An additional head protrusion is generated while the laser is on for writing, and this protrusion causes a transient clearance vary with the time constant of about 10 us (stroke is about 0.6 ~ 1 nm) which is much faster than current TFC heater, so current TFC heater cannot dynamically control/compensate the clearance variation. Therefore, we need to develop a technology to compensate the clearance change of a 0.6~1.0 nm to avoid a risk contact occurring.
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Fig.2 Illustration of clearance variation while writing with thermal flying height control heat-assisted magnetic recording technology
What are new ideas in this invention, shown in Fig.3&4?
preload interface voltage between the head and the disk
dynamically adjusting interface voltage btw head and disk to compensate the writer clear...