Recessed Spin Flipping Element for MAMR Writer Writability
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Solution Overview
Problem
Microwave Assisted Magnetic Recording (MAMR) writers face challenges with fringing growth when the spin torque oscillator (STO) bias is turned on, leading to increased reluctance in the write gap and decreased writer tracks per inch (TPI) capability due to enhanced fringing fields as the write field increases.
Innovation Solution
A spin flipping element is recessed behind the air bearing surface (ABS) in the write gap, comprising a non-spin preserving layer, a flux guiding layer with magnetization aligned in the direction of the gap field, and a spin preserving layer, which flips when a sufficient current is applied, increasing reluctance and forcing more magnetic flux through the main pole tip for enhanced writability without adverse effects on fringing field or TPI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a STO layer is inserted into the write gap and magnetization is flipped to be anti-parallel to the magnetic field in the gap, then the reluctance in the gap is increased and the write field is boosted, but fringing grows and the writer TPI capability dramatically decreases
Solution Approach 1:
The STO layer is recessed from the ABS into the write gap, transitioning from a surface-level element to a three-dimensional position within the gap. This dimensional change allows the STO to increase reluctance and boost the write field while being positioned away from the ABS to minimize fringing growth that would otherwise occur at the surface level.
Solution Approach 2:
The STO layer is positioned specifically in the write gap region between the main pole trailing side and trailing shield, with its magnetization flipped to be anti-parallel to the magnetic field in that specific location. This localized magnetization configuration increases reluctance precisely where needed to enhance the write field while controlling fringing in critical areas.
2Area of moving object
If the write head size is shrunk to increase data areal density, then smaller write heads and media bits are achieved, but writability degrades
Solution Approach 1:
The invention changes the magnetic state parameter of the STO layer by flipping its magnetization to be anti-parallel to the magnetic field in the write gap. This parameter change increases the reluctance in the gap, which compensates for the reduced writability caused by smaller write head dimensions, thereby maintaining effective writing capability despite size reduction.
3Power
If the write field is increased to improve writability, then the write field on the magnetic recording medium is enhanced, but fringing grows and TPI capability decreases
Solution Approach 1:
The invention converts the potentially harmful fringing effect into a beneficial outcome by strategically positioning the STO layer with anti-parallel magnetization in the write gap. This configuration increases reluctance to enhance the write field while the recessed positioning and localized magnetization control fringing growth, effectively converting what would be a harmful side effect into a controlled feature that supports both writability and TPI capability.
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 recessed spin flipping element reduces fringing growth and increases TPI by forcing more magnetic flux into the magnetic recording medium, maintaining writability while controlling fringing and enhancing tracks per inch capability compared to conventional MAMR designs.
Implementation Method 1
Spin transfer (spin torque) devices are based on a spin-transfer effect that arises from the spin dependent electron transport properties of ferromagnetic-non-magnetic spacer-ferromagnetic multilayers. When a spin-polarized current passes through a magnetic multilayer in a CPP (current perpendicular to plane) configuration, the magnetic moment of electrons incident on a ferromagnetic layer interacts with magnetic moments of the ferromagnetic layer near the interface between the ferromagnetic and non-magnetic spacer. Through this interaction, the electrons transfer a portion of their angular momentum to the ferromagnetic layer. As a result, spin-polarized current can switch the magnetization direction of the ferromagnetic layer if the current density is sufficiently high.
Implementation Method 2
Magnetic flux in the main pole proceeds through the ABS and into a medium bit layer and soft underlayer (SUL). In some common designs, the flux returns to the write head through a trailing side loop comprised of a trailing shield structure, and through a leading side loop that includes a leading shield and back gap connection.
Implementation Method 3
In a MAMR writer, the main pole generates a large local magnetic field to change the magnetization direction of the medium in proximity to the writer.
Data Source
AI summary
A microwave assisted magnetic recording (MAMR) writer has a recessed spin flipping element formed in the write gap between the MP tapered trailing side and a first trailing shield, a thickness ≤ to the write gap thickness, and a width ≤ to a maximum width of the MP tapered trailing side. The spin flipping element has a lower non-spin preserving layer, a middle flux guiding layer (FGL), and an upper spin preserving layer. The FGL has a magnetization that flips to a direction substantially anti-parallel to the write gap field when a current of sufficient magnitude is applied from the trailing shield towards the MP thereby increasing reluctance in the write gap and forcing additional flux out of the MP at the air bearing surface to enhance writability and tracks per inch capability on a recording medium while maintaining bits per inch capability compared with conventional MAMR writers.