Magnetic Memory Devices with In-Plane Current Layers

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Solution Overview

Problem

Conventional perpendicular-to-plane current (CPP) based magnetic tunnel junctions (pMTJs) require high switching current densities due to low efficiency in spin-transfer torque, making them inefficient for write operations.

Innovation Solution

Incorporating a heavy metal pattern adjacent to the free magnetic pattern and allowing both perpendicular-to-plane and in-plane currents to flow, which reduces switching current density by leveraging spin-orbit interaction and Rashba effect for magnetization switching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional perpendicular-to-plane current (CPP) based magnetic tunnel junctions are used, then the device structure is simple, but the switching current density is high (50-102 MA/cm²) due to low spin-transfer torque efficiency

Engineering Contradiction:

Improvedevice structureVSAvoidswitching current density

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The device is segmented into distinct functional regions: a magnetic tunnel junction region and a heavy metal pattern region. The heavy metal pattern is separated from the free magnetic layer by a tunnel barrier, creating spatially distinct current paths. This segmentation allows the application current to be divided into perpendicular-to-plane current (through the MTJ) and in-plane current (through the heavy metal pattern), enabling independent optimization of each current's contribution to magnetization switching.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces a new current dimension by adding in-plane current flow through the heavy metal pattern, complementing the conventional perpendicular-to-plane current through the MTJ. This dimensional expansion of current pathways enables dual-mode operation where in-plane current generates spin-orbit torque and perpendicular current provides spin-transfer torque, together achieving efficient magnetization switching at lower overall current densities.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Use of energy by moving object

If heavy metal pattern is added adjacent to free magnetic pattern, then switching current density is reduced to 1.2-1.8 MA/cm², but device complexity increases

Engineering Contradiction:

Improveswitching current densityVSAvoiddevice structure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The heavy metal pattern is merged with the magnetic tunnel junction structure to form an integrated magnetoresistive memory device. The heavy metal pattern is positioned adjacent to the free magnetic layer and connected through the tunnel barrier, creating a unified structure where electrical contacts can simultaneously drive both perpendicular and in-plane currents. This merging eliminates the need for separate structures while achieving low switching current density through combined spin-orbit and spin-transfer torque effects.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The heavy metal pattern serves multiple functions: it acts as a current path for in-plane current generation, provides spin-orbit torque for magnetization switching, and integrates with the MTJ structure to enable dual current mode operation. The tunnel barrier layer also serves dual purposes as both a magnetic tunnel junction barrier and an electrical connection medium between the heavy metal pattern and free magnetic layer.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution significantly reduces the switching current density from approximately 50-102 MA/cm² to 1.2-1.8 MA/cm², enhancing the efficiency of magnetization switching in pMTJs.

Implementation Method 1

allowing both perpendicular-to-plane and in-plane currents to flow, which reduces switching current density by leveraging spin-orbit interaction and Rashba effect for magnetization switching

Methodology Applied

Scientific EffectSpin-orbit interaction:

Implementation Method 2

allowing both perpendicular-to-plane and in-plane currents to flow, which reduces switching current density by leveraging spin-orbit interaction and Rashba effect for magnetization switching

Methodology Applied

Scientific EffectRashba effect:

Implementation Method 3

Resistance of the MTJ may vary depending on magnetization directions of the magnetic layers. For example, the resistance of the MTJ may be higher when magnetization directions of the magnetic layers are anti-parallel than when they are parallel

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS9882120B2Magnetic memory devices including in-plane current layers

Publication Date: 2018.01.30 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetic memory device can include an upper electrode, a lower electrode and a Magnetic Tunnel Junction (MTJ). The MTJ can include a reference magnetic pattern configured to generate a fixed magnetization and a free magnetic pattern on the reference magnetic pattern configured to generate a switchable magnetization that switches direction between parallel and anti-parallel to the fixed magnetization. A metal pattern can be on the free magnetic pattern and can be configured to conduct an in-plane current and a perpendicular-to-plane to/from the upper electrode.