TAMR Head Power Ratio Control for Wear Reduction
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Solution Overview
Problem
Thermally Assisted Magnetic Recording (TAMR) heads face challenges in accurately measuring flying height, increasing sensitivity for detecting vibrations, reducing head wear, and optimizing write-gap spacing due to thermal instabilities and sharp protrusions caused by localized heating during high-density recording.
Innovation Solution
Incorporating independently powered read and write heaters (Hr and Hw) with a power ratio (PR) control to adjust the flying height and reduce wear by using shielded read/write heads with head-disk interference sensors (HDIs) to detect touchdowns and protect against sharp protrusions, allowing for precise head-disk spacing and improved recording density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Thermally Assisted Magnetic Recording (TAMR) is used to achieve high recording density, then recording density is improved, but thermal instabilities and super-paramagnetic effects worsen
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the power ratio between read and write heaters during different operational phases. During write operations, the write heater power is increased to raise media temperature and reduce coercivity, enabling high-density recording. During read operations, the power ratio is adjusted to maintain stable head-disk spacing. This dynamic parameter adjustment resolves the contradiction between achieving high recording density and maintaining thermal stability.
2Ease of operation
If localized heating is applied to reduce media coercivity, then writing capability is improved, but sharp protrusions on the head are generated causing wear
Solution Approach 1:
The patent applies local quality by using a write heater that provides localized heating only at the write gap region where the magnetic pole contacts the media. This localized thermal field reduces coercivity precisely where needed for writing, while the read heater provides distributed heating to maintain overall head-disk spacing stability. The localized approach enables writing capability improvement without excessive overall heating that would cause head wear.
Solution Approach 2:
The patent introduces the read heater as an intermediary element that indirectly compensates for the harmful effects of write heater-induced protrusions. The read heater provides distributed thermal field that stabilizes the head-disk spacing, preventing the sharp protrusions caused by localized write heating from causing excessive wear. This intermediary thermal field mediates between the writing requirement and wear prevention.
3Productivity
If head-disk spacing is reduced to improve recording density, then recording density is improved, but flying height measurement accuracy deteriorates
Solution Approach 1:
The patent applies parameter changes by using the read heater to dynamically adjust the head-disk spacing during read operations. By controlling the read heater power, the system maintains an optimal flying height that ensures accurate touchdown detection by HDI sensors. This parameter control enables the system to achieve high recording density through reduced spacing while maintaining measurement precision through active spacing management.
4Ease of operation
If read and write heaters are independently powered with power ratio control, then head-disk spacing control is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the dual-heater system where both read and write heaters serve multiple functions. The write heater provides localized heating for coercivity reduction during writing, while also contributing to overall head-disk spacing management. The read heater provides distributed heating for spacing stability during reading, while also compensating for thermal effects from the write heater. This multi-functionality reduces the need for separate control systems, managing the complexity burden.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances TD detection accuracy, reduces head wear, and improves write performance by maintaining optimal head-disk spacing and sensitivity, while avoiding costly modifications to existing HDD systems.
Implementation Method 1
a read heater (Hr) formed adjacent to the read head and at least one write heater (Hw) formed adjacent to the write head
Implementation Method 2
adjust the flying height... maintaining optimal head-disk spacing
Implementation Method 3
head-disk interference sensors (HDIs) to detect touchdowns
Implementation Method 4
a laser diode to provide optical energy in the form of optical radiation... transfer optical energy to the surface of a magnetic recording disk
Implementation Method 5
a plasmon near-field generator located near that ABS. The plasmon generator is a device that receives the optical radiation from the waveguide, converts it to plasmon modes by electromagnetic coupling and then transfers energy from the plasmon near-fields to a small region of the recording media
Data Source
AI summary
A method of operating a HDD having a read/write head configured for Perpendicular Magnetic Recording (PMR) and configured for use in Thermally Assisted Magnetic Recording (TAMR). By using selected settings of a power ratio (PR) value to ensure that accurate fly height (FH) measurements of head-disk interference (HDI) can be taken during write touchdowns (TDs), head damage can be eliminated during HDI events. Under normal operating conditions the PMR head develops a sharp protrusion due to heating from the TAMR apparatus as well as the write current and read and write heaters. The sharp protrusion is prone to striking the disk surface, instead of the shields doing so. The shields would be more capable of absorbing the HDI, which would allow the HDI sensors (HDIs) to provide a more sensitive reading of the HDI which would prevent head wear caused by the sharp protrusion. By adjusting the power ratio (PR) to be at least the turning point (TP) value, the write shield will approach the disk surface before the sharp protrusion.