Spin Torque Oscillator With Antiparallel Stacked Layers

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Solution Overview

Problem

In high-density magnetic recording, the magnetization reversal speed of the spin injection layer in spin torque oscillators is limited by the coercive force and leakage magnetic field, leading to insufficient assisted magnetic recording due to delayed magnetization reversal and reduced spin torque tolerance.

Innovation Solution

A stacked spin injection layer with antiparallel coupled magnetization in the first and second magnetic layers, where the product of saturation magnetic flux density and film thickness of the first layer is greater than or equal to that of the second layer, and the effective magnetic anisotropy field of the first layer is higher than that of the second layer, allowing earlier magnetization reversal and enhanced spin torque tolerance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a single spin injection layer is used in the spin torque oscillator, then the structure is simple, but the magnetization reversal speed is delayed due to coercive force limitations

Engineering Contradiction:

Improvemagnetization reversal speedVSAvoidspin injection layer structure

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The spin injection layer is segmented into two magnetic layers (first magnetic layer and second magnetic layer) with antiparallel coupled magnetization. This segmentation allows the second layer to reverse magnetization earlier than a single layer would, overcoming the coercive force limitation and achieving faster magnetization reversal speed required for high-density magnetic recording.

Inventive Principle:

Principle #1Segmentation

2Speed

If the leakage magnetic field is increased to speed up magnetization reversal, then the reversal speed improves, but the spin torque tolerance is reduced

Engineering Contradiction:

Improvemagnetization reversal speedVSAvoidspin torque tolerance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The invention changes the magnetic parameters by introducing a second magnetic layer with specific saturation magnetic flux density and thickness products that are greater than or equal to the first layer. This parameter optimization enables the system to achieve fast magnetization reversal through the antiparallel coupling mechanism without requiring excessive leakage magnetic field, thereby maintaining spin torque tolerance and reliability.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a stacked spin injection layer with antiparallel coupling is used, then the magnetization reversal occurs earlier and spin torque tolerance is enhanced, but the device structure becomes more complex

Engineering Contradiction:

Improvespin torque toleranceVSAvoidstacked spin injection layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The spin injection layer is divided into two magnetic layers with antiparallel coupled magnetization. This segmentation creates a structure where the second layer can be reversed earlier by the leakage magnetic field, enhancing spin torque tolerance and enabling more reliable high-density magnetic recording despite the increased structural complexity.

Inventive Principle:

Principle #1Segmentation

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 enables longer exposure to high-frequency magnetic fields, improving recording bit stability and error rates at write speeds exceeding 1 GHz, facilitating higher recording densities.

Implementation Method 1

the discovery of a spin torque oscillator that generates microwaves by causing a magnetic material to oscillate by using spin torque

Methodology Applied

Scientific EffectSpin torque:

Implementation Method 2

A polarity of the magnetization of the second magnetic layer is reversed temporally earlier than a magnetic field polarity reversal of a leakage magnetic field from the main magnetic pole

Methodology Applied

Scientific EffectMagnetization reversal:

Implementation Method 3

Magnetization of the first magnetic layer and magnetization of the second magnetic layer are coupled antiparallel to each other

Methodology Applied

Scientific EffectAntiparallel coupling:

Implementation Method 4

a main magnetic pole that generates a recording field

Methodology Applied

Scientific EffectMagnetic field generation: Magnetic Field

Implementation Method 5

a high frequency magnetic field generation layer that generates a high frequency magnetic field

Methodology Applied

Scientific EffectHigh frequency magnetic field generation: Electromagnetic Induction

Data Source

PatentUS9007721B2Microwave assisted magnetic recording head having spin torque oscillator, and magnetic recording apparatus

Publication Date: 2015.04.14 HITACHI LTD

AI summary

A spin torque oscillator is provided which is adapted to high data transfer rates and which can perform assisted magnetic recording of sufficient magnitude. A spin torque oscillator is provided with a stacked spin injection layer and a high frequency magnetic field generation layer. The stacked spin injection layer has a stacked structure in which a first magnetic layer, a coupling layer, and a second magnetic layer are stacked in the order mentioned from a far side as viewed from the high frequency magnetic field generation layer. Magnetization of the first magnetic layer and magnetization of the second magnetic layer are coupled antiparallel to each other. A polarity of the magnetization of the second magnetic layer is reversed temporally earlier than a magnetic field polarity reversal of a leakage magnetic field from the main magnetic pole.