HAMR Magnetic Head Defect Mapping for Prohibited Sector Setting

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Solution Overview

Problem

Magnetic recording devices using heat-assisted magnetic recording (HAMR) face issues with defects on the recording medium, such as minute scratches and micro protrusions, leading to decreased thermal conductivity efficiency and magnetic recording quality due to the scraping off of a cured material formed by the magnetic head.

Innovation Solution

A magnetic recording device with a controller that detects defects on the recording medium, sets record/reproduce prohibited sectors and tracks based on defect height, and compensates for the loss of cured material by forming a cured material in a designated area to maintain thermal conductivity efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a cured material is formed on the light emitting element to increase thermal conductivity efficiency, then the temperature of the recording medium can be increased without increasing laser output, but the cured material may collide with defects on the recording surface and be scraped off, causing thermal conductivity efficiency to decrease

Engineering Contradiction:

Improvethermal conductivity efficiencyVSAvoidscraping off of cured material due to defects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by detecting defects on the recording surface before they can cause damage to the cured material. The inspection circuit identifies the position and height of defects, and the controller pre-determines prohibited recording areas based on this information, preventing the cured material from being scraped off before it can perform its thermal conductivity function

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful effect of defects into a beneficial outcome by using the defect information to establish prohibited recording areas. Instead of allowing defects to scrape off the cured material and degrade performance, the system uses defect detection to proactively avoid those areas, thereby protecting the cured material and maintaining thermal conductivity efficiency

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Quantity of substance

If recording is performed on all tracks and sectors, then recording capacity is maximized, but recording quality degrades when the magnetic head passes over defects on the recording surface

Engineering Contradiction:

Improverecording capacityVSAvoidmagnetic recording quality

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent applies segmentation by dividing the recording surface into permitted and prohibited recording areas based on defect locations. The controller sets specific tracks and sectors as prohibited areas where recording is avoided, while allowing recording in permitted areas, thus segmenting the recording space to maintain quality while preserving overall capacity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by applying different recording policies to different regions of the recording surface. Instead of uniformly recording across all areas, the system applies prohibited recording designations locally to specific tracks and sectors containing defects, while maintaining normal recording operations in defect-free areas, thereby preserving both quality and capacity

Inventive Principle:

Principle #3Local quality

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

The solution effectively prevents degradation of recording quality and improves recording density by setting prohibited areas and forming a cured material to maintain thermal conductivity efficiency, even in the presence of defects.

Implementation Method 1

HAMR is a technology of increasing the recording capacity by heating a recording medium with a laser during recording

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

This cured material functions as a layer that increases the thermal conductivity efficiency of the laser beam

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS12475930B1Magnetic recording device

Publication Date: 2025.11.18 KK TOSHIBA

AI summary

According to one embodiment, a magnetic recording device includes a recording medium, a magnetic head including a light source, a light emitting element, and a sensor, and a controller including an inspection circuit which detects a height of a defect of the recoding medium based on output of the sensor, a memory recording the height of the defect, and a setting circuit which sets an upstream side record/reproduce prohibited sector on an upstream side of the defect, in a travel direction of the magnetic head, on a track of the recording medium on which the defect is present, and which sets a downstream side record/reproduce prohibited sector longer in track direction than the upstream side record/reproduce prohibited sector on a downstream side of the defect.