HAMR Write Current Control via Effective Thermal Spot Size
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) systems, existing writing operations face challenges with data reliability due to high coercivity of the magnetic medium, leading to issues like superparamagnetic effects and adjacent track interference, especially when using short symbol lengths which may not allow sufficient time for adequate magnetization and reliable read operations.
Innovation Solution
The method involves generating a sequence of symbols of length nT, where T is a channel clock rate, and using a near-field transducer to produce a thermal spot with an effective thermal spot size (ETSS) to apply bi-directional write currents to the write pole, with the duration of current application dependent on the symbol length and ETSS, allowing for efficient data recording by reducing adjacent track and down-track erasure, and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If short symbol lengths are used for data recording, then storage density is improved, but data reliability deteriorates due to insufficient magnetization time and superparameteric effects
Solution Approach 1:
The patent changes the physical state of the magnetic medium by heating it to high temperature during the write operation. This temperature change reduces the coercivity of the medium, allowing short symbol lengths to be reliably recorded. The thermal assistance enables adequate magnetization even for brief current pulses corresponding to short symbols, thereby maintaining data reliability while achieving high storage density.
Solution Approach 2:
The patent employs periodic heating cycles where the laser heats the medium just before and during the write current pulse, then cools it afterward. This periodic thermal action creates optimal conditions for each write operation: high temperature during writing for low coercivity and reliable magnetization of short symbols, followed by cooling to restore high coercivity for data stability during reading operations.
2Reliability
If high write currents are applied for extended durations to ensure adequate magnetization, then data reliability is improved, but power consumption increases
Solution Approach 1:
The patent changes the temperature parameter of the magnetic medium during the write operation. By heating the medium to high temperature, the coercivity is reduced, which allows the same magnetic flux change to be achieved with shorter current pulses or lower current amplitudes. This thermal parameter change enables reliable magnetization with reduced energy input compared to cold writing with extended current durations.
Solution Approach 2:
The patent applies preliminary heating to the magnetic medium before applying the write current. This preliminary thermal action reduces the coercivity in advance, so that when the write current is applied, the medium is already in a state that requires less energy for magnetization. The combination of pre-heating and brief current application achieves reliable writing with lower overall power consumption than prolonged current application at room temperature.
3Device complexity
If conventional writing operations are used without thermal assistance, then device complexity is reduced, but adjacent track interference and down-track erasure increase
Solution Approach 1:
The patent applies thermal energy locally to a small spot on the magnetic medium using a focused laser beam delivered through a near-field transducer. This localized heating creates a small region of reduced coercivity exactly where the write current is applied. The thermal spot is confined to a diameter of about 50-100 nm, ensuring that only the intended track area is affected. This local thermal quality change enables precise writing with minimal adjacent track interference, as the thermal and magnetic fields are both spatially confined to the same small region.
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 approach enhances data recording reliability, reduces adjacent track and down-track erasure, shortens magnetic rise-time, and lowers power consumption by optimizing write current application based on the effective thermal spot size and symbol length, thereby improving data storage density and consistency.
Implementation Method 1
producing a thermal spot on a magnetic storage medium using a near-field transducer situated proximate a write pole
Implementation Method 2
heat-assisted magnetic recording (HAMR) systems, existing writing operations face challenges with data reliability due to high coercivity of the magnetic medium
Data Source
AI summary
A heat-assisted magnetic recording device includes a write pole positionable adjacent a magnetic recording medium and configured to write data to the medium. A near-field transducer is situated proximate the write pole and configured to produce a thermal spot on the medium. A channel circuit is configured to generate a sequence of symbols having a length of nT, where T is a channel clock rate and n is an integer over a predetermined range. A write driver is configured to apply bi-directional write currents to the write pole to record the sequence of symbols at a location of the thermal spot on the medium, wherein a duration of applying the write currents to the write pole by the write driver is dependent on a length of the sequence of symbols and the effective thermal spot size.