Spin-Torque Oscillator Polarization Layout for Stronger AC Fields

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Solution Overview

Problem

Existing microwave assisted magnetic recording (MAMR) heads face inefficiencies due to partial cancellation of magnetizations in spin torque oscillators (STOs) with anti-parallel magnetization configurations, leading to weak AC magnetic fields.

Innovation Solution

Incorporating a negative polarization material in one magnetic layer and a positive polarization material in the other layer of the STO, with an interlayer in between, to ensure parallel magnetization directions and strengthen the AC magnetic field.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If anti-parallel magnetization directions are used in SPL and FGL, then oscillation with small bias current is obtained, but magnetizations partially cancel leading to weak AC magnetic field

Engineering Contradiction:

Improvebias currentVSAvoidAC magnetic field

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The patent inverts the conventional anti-parallel magnetization configuration by using parallel magnetization directions in both SPL and FGL. This inversion resolves the contradiction by preventing magnetization cancellation while maintaining efficient spin torque transfer, thereby generating a stronger AC magnetic field without requiring excessive bias current.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the magnetization configuration parameter from anti-parallel to parallel alignment between SPL and FGL. This parameter change fundamentally alters the magnetic field generation mechanism, eliminating the cancellation effect while preserving the spin torque oscillation efficiency, thus achieving both low bias current operation and strong AC magnetic field output.

Inventive Principle:

Principle #35Parameter changes

2Strength

If parallel magnetization directions are used in SPL and FGL, then AC magnetic field is strengthened, but spin torque transfer efficiency may be reduced

Engineering Contradiction:

ImproveAC magnetic fieldVSAvoidspin torque transfer efficiency

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent introduces a non-magnetic interlayer as an intermediary between the SPL and FGL. This interlayer facilitates efficient spin torque transfer from the SPL to the FGL while allowing the magnetizations in both layers to be oriented in the same direction. The interlayer acts as a mediator that decouples the magnetization orientation from the spin torque transfer mechanism, resolving the contradiction between field strength and transfer efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration suppresses the cancellation of magnetizations, resulting in a stronger AC magnetic field for improved recording quality in MAMR heads.

Implementation Method 1

the STO generates high frequency magnetic fields, or microwaves, as a result of the transfer of spin torque from the SPL through the interlayer to the FGL

Methodology Applied

Scientific EffectSpin torque:

Implementation Method 2

the STO oscillates and may provide an AC magnetic field to the recording medium

Methodology Applied

Scientific EffectMagnetization oscillation:

Implementation Method 3

The AC magnetic field may reduce the coercive force of the recording medium, thus high quality recording by MAMR may be achieved

Methodology Applied

Scientific EffectCoercive force reduction:

Data Source

PatentUS9305574B1Negative-polarization spin-torque-oscillator

Publication Date: 2016.04.05 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

Embodiments disclosed herein generally relate to a MAMR head. The MAMR head includes an STO. The STO has a first magnetic layer, a second magnetic layer and an interlayer disposed between the first and second magnetic layers. One of the first and second magnetic layers is made of a negative polarization material while the other magnetic layer is made of a positive polarization material. As a result, the magnetizations in the first and second magnetic layers are in the same direction when in oscillation, which suppresses the partial cancellation of the magnetizations in the first and second magnetic layers and strengthens the AC magnetic field.