Magnetic Junctions With Tilted Easy Axes for Reliable Spin Orbit Torque Switching

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Solution Overview

Problem

Conventional magnetic memories, such as SO torque-based MRAMs, face challenges in reliable switching of magnetic moments, especially in smaller junction sizes and higher areal density memories, due to the need for external magnetic fields and limited efficiency of SO torque mechanisms.

Innovation Solution

The implementation of magnetic junctions with a tilted easy axis and high damping constant, where the free layer has a nonzero acute angle from the perpendicular-to-plane direction and a damping constant of at least 0.02, allowing for reliable switching using in-plane SO torque without the need for external magnetic fields or biases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional magnetic junctions use in-plane current for writing, then SO torque can be generated, but external magnetic fields are required for reliable switching

Engineering Contradiction:

ImproveSO torque generationVSAvoidswitching reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the magnetic anisotropy parameter of the free layer from in-plane to perpendicular-to-plane orientation. This parameter change enables the free layer to be switched by SO torque generated from in-plane current without requiring external magnetic fields, thereby improving switching reliability while maintaining power efficiency.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If external magnetic fields are applied for switching, then reliable state selection is achieved, but additional current-carrying lines and complexity are required

Engineering Contradiction:

Improvestate selectionVSAvoidcurrent-carrying lines

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the requirement for external magnetic fields and additional current-carrying lines by utilizing perpendicular-to-plane magnetization in the free layer. The SO torque from the existing in-plane current line is sufficient to switch the magnetization state, removing the need for separate write and read current paths and simplifying the device structure.

Inventive Principle:

Principle #2Taking out (Extraction)

3Area of stationary object

If smaller magnetic junction sizes are used, then higher areal density is achieved, but switching reliability deteriorates

Engineering Contradiction:

Improvejunction sizeVSAvoidswitching reliability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent changes the magnetization orientation parameter to perpendicular-to-plane, which fundamentally alters the switching mechanism. This parameter change enables reliable switching in smaller junction sizes because the SO torque efficiency is improved and the switching process becomes less sensitive to junction size reductions, allowing higher areal density without sacrificing reliability.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If AFM layers or biasing structures are added, then magnetic bias is provided, but SO torque efficiency is limited

Engineering Contradiction:

Improvemagnetic biasVSAvoidSO torque efficiency

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent removes the AFM layer and biasing structure from the magnetic junction. By utilizing perpendicular-to-plane magnetization in the free layer, the system achieves reliable switching without these additional components, thereby eliminating the limitation on SO torque efficiency that these structures impose while still providing the necessary magnetic bias through the perpendicular anisotropy.

Inventive Principle:

Principle #2Taking out (Extraction)

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 approach enables faster and more reliable switching of magnetic moments, reducing the risk of damage to the junctions and eliminating the need for additional current-carrying lines, thereby improving the performance and efficiency of magnetic memories.

Implementation Method 1

The high spin-orbit interaction may be due to a bulk effect of the material itself (spin Hall effect)

Methodology Applied

Scientific EffectSpin Hall Effect: Hall Effect

Implementation Method 2

due to interfacial interactions (Rashba effect)

Methodology Applied

Scientific EffectRashba Effect:

Implementation Method 3

The free layer has at least one of a tilted easy axis and a high damping constant. The tilted easy axis is at a nonzero acute angle from a direction perpendicular-to-plane

Methodology Applied

Scientific EffectMagnetic Anisotropy: Anisotropy

Data Source

PatentUS10121961B2Magnetic devices including magnetic junctions having tilted easy axes and enhanced damping programmable using spin orbit torque

Publication Date: 2018.11.06 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetic memory including a plurality of magnetic junctions and at least one spin-orbit interaction (SO) active layer is described. Each of the magnetic junctions includes a pinned layer, a free layer and a nonmagnetic spacer layer between reference and free layers. The free layer has at least one of a tilted easy axis and a high damping constant. The tilted easy axis is at a nonzero acute angle from a direction perpendicular-to-plane. The high damping constant is at least 0.02. The at least one SO active layer is adjacent to the free layer and carries a current in-plane. The at least one SO active layer exerts a SO torque on the free layer due to the current. The free layer is switchable using the SO torque.