HAMR Disk With Independent Magnetic Layers
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Solution Overview
Problem
Conventional magnetic recording hard disk drives face thermal instability issues due to the thermal dependence of magneto-crystalline anisotropy, leading to data loss, and existing heat-assisted magnetic recording (HAMR) systems require vertical alignment of data bits across multiple layers, which is not feasible with continuous non-patterned media.
Innovation Solution
A HAMR disk with multiple independent continuous non-patterned magnetic recording layers, each separated by a nonmagnetic spacer layer, allowing for independent data storage without vertical alignment, where the coercivity of each layer is greater than the write field at ambient temperature, and the Curie temperature can be selectively exceeded by varying the laser power to record data in one or both layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high magneto-crystalline anisotropy (Ku) is used to avoid thermal instability, then thermal stability of recorded data is improved, but coercivity increases beyond the write field capability of the write head
Solution Approach 1:
The patent changes the temperature parameter during the writing process. By heating the recording layer to a Curie temperature where coercivity is reduced, the write head can successfully write data. After writing, the layer cools back to ambient temperature where high coercivity provides thermal stability. This temporal parameter change resolves the contradiction between high coercivity needed for stability and low coercivity needed for writing.
Solution Approach 2:
The writing process employs periodic heating and cooling cycles. The recording layer is periodically heated to reduce coercivity for writing, then cooled to restore high coercivity for stability. This periodic thermal action allows the system to alternate between the two opposing states (high coercivity for stability, low coercivity for writing) as needed.
2Quantity of substance
If multiple magnetic recording layers are stacked to increase data density, then storage capacity is improved, but vertical alignment of data bits across layers becomes required
Solution Approach 1:
The patent segments the multiple magnetic recording layers into independent units by introducing nonmagnetic spacer layers between them. Each recording layer can be independently written to and read from without requiring vertical alignment with other layers. The spacer layers act as magnetic isolation barriers, allowing each layer to function as an independent storage medium while maintaining physical proximity for high density.
Solution Approach 2:
The nonmagnetic spacer layers serve as intermediary elements between adjacent magnetic recording layers. These spacers magnetically decouple the layers, preventing magnetic interaction between them and eliminating the need for vertical alignment. The intermediaries allow independent operation of each layer while maintaining the stacked structure for increased capacity.
3Ease of operation
If laser power is increased to heat both recording layers above Curie temperature for simultaneous writing, then writing capability is improved, but energy consumption increases and thermal management becomes more difficult
Solution Approach 1:
The patent applies partial heating action by allowing the operator to select different laser power levels. At lower power levels, only the upper recording layer is heated above its Curie temperature for selective writing. At higher power levels, both layers are heated for simultaneous writing. This partial action approach allows energy consumption to be matched to the actual writing needs, avoiding unnecessary energy expenditure.
Solution Approach 2:
The system dynamically adjusts laser power levels based on writing requirements. The laser power can be varied in real-time to match the specific operation: low power for writing only the upper layer, high power for writing both layers simultaneously. This dynamic control optimizes energy consumption by applying only the necessary heating power for each specific writing task.
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 solution ensures high thermal stability of recorded magnetic bits and allows for independent data storage in each layer without the need for vertical alignment, enhancing data density and operational reliability.
Implementation Method 1
The SL has a thermal conductivity and thickness that prevents lower RL1 from being heated to near or above its Curie temperature (TC1) when the laser is operating at a lower power level (PL)
Implementation Method 2
If the laser is operating at a higher power level (PH) that heats both RL1 and RL2 to above their respective Curie temperatures, data is recorded in both RL1 and RL2
Data Source
AI summary
A heat-assisted magnetic recording (HAMR) disk has multiple independent data layers, each data layer being a continuous non-patterned layer of magnetizable material. Each data layer can store data independent and not related to the data stored in the other data layers. The data layers are separated by a nonmagnetic spacer layer (SL) and each data layer is formed of high-anisotropy (Ku) material so that the coercivities of lower and upper data layers (RL1 and RL2) are greater than the magnetic write field. At a high laser power both RL1 and RL2 are heated to above their respective Curie temperatures and data is recorded in both RL1 and RL2. At low laser power only upper RL2 is heated to above its Curie temperature and data is recorded only in RL2. The SL prevents lower RL1 from being heated to above its Curie temperature at low laser power.