Thermally Unstable Reference Layer Magnetic Memory for Density Scaling

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Solution Overview

Problem

Conventional spin transfer torque based magnetic memories face challenges in scaling to higher densities due to asymmetric write currents, larger storage cell sizes, and thermal stability issues, which hinder their potential for high density, fast operation, and low power consumption.

Innovation Solution

A magnetic memory system utilizing a magnetic element with a thermally unstable reference layer and a thermally stable free layer, allowing switching with a unidirectional write current and external magnetic field, to achieve smaller storage cell sizes and improved thermal stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional spin transfer torque based magnetic memories are used, then fast operation and non-volatility are achieved, but thermal stability issues and asymmetric write currents prevent scaling to higher densities

Engineering Contradiction:

Improvestorage densityVSAvoidthermal stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the thermal stability parameter (KuV/kBT) of the reference layer from the conventional stable state (≥55) to an unstable state (<55). This parameter change enables the reference layer to be reset by thermal energy at operating temperatures, allowing unidirectional write currents and enabling scaling to higher densities while maintaining reliability through controlled thermal behavior

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent inverts the conventional approach by making the reference layer thermally unstable rather than stable. Conventionally, the reference layer is designed to be thermally stable to maintain its magnetization direction, but this invention deliberately makes it unstable so that thermal energy can reset the layer, enabling new writing mechanisms and higher density scaling

Inventive Principle:

Principle #13The other way round (Inversion)

2Area of stationary object

If conventional magnetic elements with thermally stable reference layers are used, then data retention is maintained, but unidirectional writing capability and smaller storage cell sizes cannot be achieved

Engineering Contradiction:

Improvestorage cell sizeVSAvoidreference layer magnetization stability

Core Design Contradiction:

Area of stationary objectVSStability of the object's composition

Solution Approach 1:

The patent introduces dynamic behavior to the reference layer by making its magnetization thermally switchable. The reference layer transitions from a static, permanently stable magnetization state to a dynamic state where thermal energy can flip the magnetization direction. This dynamic capability enables the layer to be reset during writing operations, allowing smaller storage cell sizes and unidirectional writing while maintaining data retention through controlled stability

Inventive Principle:

Principle #15Dynamics

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

Enables the magnetic memory to be scaled to higher densities with smaller storage cells, maintaining fast operation and low power consumption, while enhancing thermal stability without increasing the spin transfer torque switching current density.

Implementation Method 1

the magnetic element is configured to allow the free layer to be switched to each of a plurality of states when a write current is passed through the magnetic element

Methodology Applied

Scientific EffectSpin transfer torque:

Implementation Method 2

The reference layer has a resettable magnetization that is set in a selected direction by a magnetic field generated externally to the reference layer

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Data Source

PatentUS7800942B2Method and system for providing a magnetic element and magnetic memory being unidirectional writing enabled

Publication Date: 2010.09.21 RENESAS ELECTRONICS CORP

AI summary

A method and system for providing a magnetic element and memory utilizing the magnetic element are described. The magnetic element includes a reference layer, a nonferromagnetic spacer layer, and a free layer. The reference layer has a resettable magnetization that is set in a selected direction by a magnetic field generated externally to the reference layer. The reference layer is also magnetically thermally unstable at an operating temperature range and has KuV/kBT is less than fifty five. The spacer layer resides between the reference layer and the free layer. In addition, the magnetic element is configured to allow the free layer to be switched to each of a plurality of states when a write current is passed through the magnetic element.