Negative Spin Polarization STO for STRAMR Write Field

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Solution Overview

Problem

Current spin torque (STO) devices in spin transfer torque reversal assisted magnetic recording (STRAMR) require high current densities for effective write field enhancement, which can compromise device reliability and increase bit error rates, and existing designs often necessitate additional layers or complex processes.

Innovation Solution

A STO device configuration with a flux guiding layer (FGL) and spin injection layer (SIL) having negative or weakly positive spin polarization materials, allowing for greater FGL magnetization flipping and write field enhancement at reduced current densities, while maintaining or improving bit error rates without requiring significant additional layers or process steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high current density is applied to achieve effective write field enhancement in STRAMR, then write field enhancement is improved, but device reliability deteriorates and bit error rates increase

Engineering Contradiction:

Improvewrite field enhancementVSAvoiddevice reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the spin polarization parameter of the SIL and FGL materials from conventional positive polarization (≥0.4) to negative or weakly positive polarization (−0.4 to 0.3). This parameter change enables effective FGL magnetization flipping and write field enhancement at reduced current densities, thereby improving device reliability while maintaining write field enhancement capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures with specific spin polarization characteristics in the SIL and FGL layers. By selecting materials with negative or weakly positive spin polarization, the device achieves enhanced spin torque efficiency, enabling effective operation at lower current densities and improving overall device reliability

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional SIL and FGL materials with positive spin polarization are used, then device reliability is maintained, but FGL magnetization flipping extent is limited at given current density

Engineering Contradiction:

Improvedevice reliabilityVSAvoidFGL flipping extent

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent fundamentally changes the spin polarization parameter from positive (≥0.4) to negative or weakly positive (−0.4 to 0.3). This parameter inversion enhances the spin torque effect on FGL magnetization, resulting in greater flipping extent at the same current density while maintaining acceptable device reliability through careful material selection

Inventive Principle:

Principle #35Parameter changes

3Power

If additional layers are added to improve write field enhancement, then write capability is improved, but fabrication process complexity increases

Engineering Contradiction:

Improvewrite field enhancementVSAvoidfabrication process complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

Instead of adding structural complexity through additional layers, the patent achieves improved write field enhancement by changing the material parameters (spin polarization) of existing SIL and FGL layers. This approach maintains the original device structure and fabrication process simplicity while achieving the desired performance improvement through material selection

Inventive Principle:

Principle #35Parameter changes

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 proposed STO device achieves enhanced write field and reduced bit error rates with lower current densities, improving device reliability and writability without increasing the complexity of the fabrication process.

Implementation Method 1

spin transfer torque reversal assisted magnetic recording (STRAMR) wherein a flux guiding layer (FGL) magnetization flips to an opposite direction that opposes the WG magnetic field as a result of spin torque from an adjacent spin polarization (SP) layer and from an adjacent spin injection layer (SIL) when a current (Ia) of sufficient density is applied across the STO device

Methodology Applied

Scientific EffectSpin transfer torque:

Implementation Method 2

MAMR uses a spin torque device to generate a high frequency field that reduces the coercive field of a medium bit thereby allowing the bit to be switched with a lower main pole field

Methodology Applied

Scientific EffectMicrowave assisted magnetic recording:

Data Source

PatentUS10937450B1Magnetic flux guiding device with spin torque oscillator (STO) film having one or more negative spin polarization layers in assisted writing application

Publication Date: 2021.03.02 HEADWAY TECHNOLOGIES INC

AI summary

A spin transfer torque reversal assisted magnetic recording (STRAMR) device is disclosed wherein a flux guiding layer (FGL) magnetization flips to an opposite direction opposing the write gap (WG) field because of spin torque from an adjacent spin polarization (SP) layer and spin injection layer (SIL) when a current (Ia) of sufficient density is applied across the device and between the main pole (MP) and trailing shield (TS) thereby enhancing the MP write field. The SP layer adjoins the MP or TS and maintains a magnetization in the WG field direction. One or both of the SIL and FGL has a spin polarization from −0.4 to 0.3 and may be doped with C, N, or B so that the extent of FGL flipping is greater at a given current density than in the prior art where all magnetic layers within the STRAMR device have a positive spin polarization ≥0.4.