Microwave-Assisted Magnetic Head Write Gap Design
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Solution Overview
Problem
The challenge in magnetic recording is to enhance recording density while maintaining thermal stability of magnetic grains, as reducing grain size decreases thermal stability and increasing magnetic anisotropy energy limits the recording magnetic field intensity.
Innovation Solution
A microwave assisted magnetic head with a write gap structure that includes a central first write gap part and extended second and third write gap parts in the cross track direction, allowing for increased magnetic field intensity and gradient, thereby improving oscillation frequency and recording density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of magnetic grains is reduced to enhance recording density, then recording density is improved, but thermal stability of magnetization is reduced
Solution Approach 1:
The patent changes the magnetic anisotropy energy parameter by using perpendicular magnetization instead of in-plane magnetization. This parameter change allows smaller magnetic grains to maintain thermal stability because perpendicular magnetization provides higher magnetic anisotropy energy, preventing superparamagnetic effects in reduced-size grains while enabling higher recording density.
2Reliability
If magnetic anisotropy energy Ku is increased to improve thermal stability, then thermal stability is improved, but anisotropic magnetic field (coercive force) increases beyond the upper limit of recording magnetic field intensity
Solution Approach 1:
The patent changes the magnetization direction parameter from in-plane to perpendicular orientation. This parameter change allows the magnetic recording medium to achieve high thermal stability through increased magnetic anisotropy energy while the recording magnetic head can still write effectively because the perpendicular magnetization geometry changes the relationship between applied field and coercive force, allowing recording at lower field intensities.
3Speed
If the write gap is narrowed to improve oscillation frequency of STO, then oscillation frequency is improved, but there is a limitation to how much the write gap can be narrowed
Solution Approach 1:
The patent applies local quality by creating non-uniform gap structures where different regions have different gap widths. The write gap is narrowed in specific locations where STO is positioned to maximize oscillation frequency and magnetic field intensity, while other regions maintain larger gaps to prevent interference and allow proper magnetic flux distribution. This localized optimization resolves the contradiction between narrowing the gap and maintaining device functionality.
4Productivity
If track width is narrowed to improve recording density, then recording density is improved, but signals in adjacent tracks may be erased
Solution Approach 1:
The patent uses local quality by creating position-dependent gap structures that optimize magnetic field confinement. In regions where tracks are closely spaced, the gap structure is designed to concentrate and confine the magnetic field more tightly to the intended track, preventing field leakage into adjacent tracks. This localized field control allows narrower track widths for higher density while preventing harmful erasure effects in neighboring tracks.
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 enhances magnetic field intensity applied to the spin torque oscillator, improving recording density by steepening the magnetic field gradient, preventing signal erasure in adjacent tracks, and achieving high bit and track per inch performance.
Implementation Method 1
a spin torque oscillator that is disposed within the write gap so as to be interposed between the main magnetic pole and the trailing shield, and that generates a microwave magnetic field to be superimposed on the magnetic recording field applied to the magnetic recording medium
Implementation Method 2
The STO generates a microwave magnetic field in the in-plane direction by its self-oscillation. Precession movement of the magnetization of the recording layer is excited by applying the microwave magnetic field to the magnetic recording medium
Implementation Method 3
the application of the microwave magnetic field in the medium in-plane direction of a frequency according to an effective magnetic field (Heff) relating to magnetization of a recording layer in the magnetic recording medium excites precession movement of the magnetization of the recording layer, and recording capability of a magnetic head is assisted
Implementation Method 4
a main magnetic pole that generates a recording magnetic field to be applied to a magnetic recording medium from an end surface constituting a portion of an air bearing surface opposed to the magnetic recording medium
Data Source
AI summary
A microwave assisted magnetic head is equipped with a main magnetic pole that generates a recording magnetic field to be applied to a magnetic recording medium from an end surface forming a portion of an air bearing surface opposed to the magnetic recording medium, a trailing shield that is disposed interposing a write gap at a trailing side of the main magnetic pole, and that forms a magnetic path with the main magnetic pole, two side shields that are disposed at both sides of the main magnetic pole in the cross track direction, respectively, and a spin torque oscillator that is disposed within the write gap. The write gap is configured to substantially linearly extend along the cross track direction when viewed from an air bearing surface side, and is positioned between trailing-side end surfaces of the main magnetic pole and the two side shields, and a leading-side end surface of the trailing shield.