Heat-Assisted Narrow Pole With Trailing Shield
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Solution Overview
Problem
Current magnetic recording technologies face challenges in achieving high areal densities due to conflicting requirements of stronger writing fields and smaller write heads, which lead to thermal instability and adjacent track erasures, especially when using high coercivity and anisotropy media like FePt.
Innovation Solution
A heat-assisted narrow magnetic pole with a trailing shield and edge plasmon generator is used to locally heat the magnetic medium below its Curie temperature, allowing for high areal densities on existing PMR media with slightly higher Hk, without causing significant adjacent track erasures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a smaller write head is used to achieve high areal densities, then the track width is reduced and recording density is improved, but the field gradient decreases and field profile broadens, reducing writing capability
Solution Approach 1:
The patent applies thermal heating to change the magnetic properties of the medium temporarily. By raising the temperature of the medium in the recording region, the coercivity and anisotropy are reduced, enabling easier magnetic writing with the narrowed pole tip structure. This parameter change (temperature) allows the system to overcome the reduced field gradient issue.
Solution Approach 2:
The patent introduces thermal energy as an intermediary mechanism between the write head and the magnetic medium. The heating element acts as a mediator that modifies the magnetic properties of the medium, facilitating the writing process despite the narrower pole tip geometry that would otherwise produce insufficient field gradient.
2Reliability
If high coercivity and anisotropy media are used to delay superparamagnetic effect, then thermal stability is improved, but stronger writing field is required, conflicting with smaller write head capability
Solution Approach 1:
The patent temporarily changes the temperature parameter of the magnetic medium to reduce its coercivity and anisotropy during the writing process. This allows standard field strengths to effectively write on high-coercivity media, after which the medium cools and regains its high thermal stability for data retention.
Solution Approach 2:
The heating is applied periodically or locally only during the writing operation, not continuously. The medium is heated briefly to enable writing, then returns to its normal temperature state to maintain thermal stability, creating a periodic cycle of modified and normal magnetic properties.
3Ease of operation
If laser heating is applied to raise medium temperature to Curie temperature, then magnetic writing becomes easier, but adjacent track erasures occur and laser power requirements increase
Solution Approach 1:
The patent confines the heating to a very localized region directly under the pole tip using the narrow plasmon-generated spot. This local quality approach ensures that only the immediate recording region is heated, preventing thermal diffusion to adjacent tracks and eliminating the cause of adjacent track erasures while maintaining effective writing conditions at the target location.
Solution Approach 2:
The patent replaces conventional broad thermal heating methods with plasmon-mediated localized heating. This substitution enables precise spatial control of the thermal field, concentrating energy exactly where needed and avoiding the harmful thermal spread that causes adjacent track erasures in traditional heating approaches.
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
This design enables high linear and areal densities (>1500 kbpi) with moderately elevated temperatures, improving thermal stability and reducing laser power requirements, while maintaining good transition writability and narrow track widths.
Implementation Method 1
The edge plasmon mode is excited in an overlap region between a conducting plasmon generator (PG) and a waveguide (WG)... the light optical mode couples to a propagating plasmon mode of a PG, whereby the optical energy is converted into plasmon energy
Implementation Method 2
This plasmon energy is then transferred to the medium at the pole tip, at which point the heating occurs at a very small spot size... raising the temperature of a small region of the magnetic medium to essentially its Curie temperature (Tc)
Implementation Method 3
raising the temperature of a small region of the magnetic medium to essentially its Curie temperature (Tc), at which temperature both its coercivity and anisotropy are significantly reduced
Data Source
AI summary
A TAMR (Thermally Assisted Magnetic Recording) write head is formed with a narrow pole tip, a trailing edge magnetic shield and, optionally, a plasmon shield. The narrow pole tipped write head uses the energy of laser generated edge plasmons, formed in a plasmon generating layer, to locally heat a PMR magnetic recording medium slightly below its Curie temperature, Tc. When combined with the effects of the narrow tip, this local heating to a temperature below Tc is sufficient to create good transitions and narrow track widths in the magnetic medium. The write head is capable of writing effectively on state-of-the-art PMR recording media having Hk of 20 kOe or more.