HAMR Slider Laser Beam Shaping and Waveguide Integration
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Solution Overview
Problem
The challenge of achieving high areal bit densities in magnetic storage is hindered by superparamagnetic instabilities in small grain media, where thermal energy can demagnetize data due to insufficient magnetocrystalline anisotropy energy density, and existing recording heads struggle to provide sufficient magnetic writing fields.
Innovation Solution
An integrated heat-assisted magnetic recording (HAMR) device is developed, comprising a slider with a laser, beam shaper, mirror, waveguide, and near field transducer, which locally heats the magnetic medium using electromagnetic waves to reduce coercivity and enhance thermal stability, allowing for smaller grain sizes and higher areal densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the grain volume of the recording medium is reduced to increase areal density, then the areal bit density increases, but superparameteric instabilities cause thermal demagnetization
Solution Approach 1:
The patent changes the temperature parameter dynamically during the recording process. By heating the recording medium to elevated temperatures during writing, the coercivity is reduced allowing successful recording. After cooling, the high coercivity at room temperature provides thermal stability. This temporal parameter change resolves the contradiction between small grain size and thermal stability.
Solution Approach 2:
The recording process employs periodic thermal cycles - heating during writing and cooling during reading/storage. This periodic action allows the system to exploit high-temperature low-coercivity states for writing and low-temperature high-coercivity states for stable storage, resolving the contradiction between writability and thermal stability.
2Reliability
If a material with very high Ku is used to improve thermal stability, then thermal stability improves, but recording heads cannot provide sufficient magnetic writing field
Solution Approach 1:
The patent changes the temperature parameter during writing to temporarily reduce coercivity. By heating the medium, the effective coercivity drops from very high values to lower values that can be overcome by conventional recording head fields, while maintaining high Ku material for overall thermal stability.
Solution Approach 2:
The patent applies preliminary heating to the recording medium before applying the magnetic writing field. This preliminary thermal action softens the magnetic properties, enabling subsequent writing with available head fields, while the high Ku material ensures stability after cooling.
3Use of energy by moving object
If optical fibers are used for light delivery in HAMR, then light delivery efficiency improves, but the stiff optical fibers affect slider flyability
Solution Approach 1:
The patent extracts the optical fiber from the slider assembly and places it in the actuator assembly instead. This separation removes the stiff fiber from the flyable slider, eliminating the flyability problem while maintaining light delivery functionality through a different mounting location.
Solution Approach 2:
The patent introduces a flexible waveguide as an intermediary between the actuator-mounted optical fiber and the slider. This flexible intermediate component transmits light while accommodating the movement and positioning requirements of the flying slider, resolving the conflict between rigid fiber and flexible slider operation.
4Ease of manufacture
If the laser is positioned far from the waveguide to simplify mounting, then ease of manufacture improves, but light delivery efficiency decreases
Solution Approach 1:
The patent uses a waveguide structure that extends in space to bridge the gap between the laser and the recording spot. By utilizing the spatial dimension and the waveguide's light-confining properties, the system maintains efficient light delivery over longer distances, decoupling manufacturing ease from efficiency requirements.
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 HAMR device enables stable data storage at increased areal densities by effectively directing magnetic fields to small grain media, ensuring thermal stability through localized heating, thus overcoming the limitations of conventional recording heads.
Implementation Method 1
an electromagnetic wave of, for example, visible, infrared, or ultraviolet light can be directed onto a surface of a data storage medium to raise the temperature of a localized area
Implementation Method 2
Well known optical waveguides such as solid immersion lenses (SILs), solid immersion mirrors (SIMs), and mode index lenses have been proposed for use in reducing the size of a spot on the medium that is subjected to the electromagnetic radiation
Implementation Method 3
Metal pins and other near field transducer (NFT) designs positioned at the focal point of the waveguide are used to further concentrate the energy and direct it to a small spot on the surface of the recording medium
Implementation Method 4
The beam shaper is attached to the slider such that the light beam from the laser is collimated or focused
Implementation Method 5
The mirror is attached to the slider such that the mirror directs the collimated or focused light beam into a waveguide mounted on the slider
Data Source
AI summary
An integrated heat-assisted magnetic recording (HAMR) device comprises a slider that has a top surface, a bottom surface, and a trailing end. A waveguide is carried on the trailing end and a near field transducer is positioned to receive energy from the waveguide and produce plasmons for heating a region of a magnetic medium. A write pole is carried by the slider adjacent to the near field transducer. A laser is mounted on the top surface of the slider and produces a laser beam that passes through a beam shaper mounted on the top surface of the slider that collimates or focuses the laser beam. A mirror is mounted on the slider for directing the collimated or focused light beam into the waveguide.