Perpendicular Magnetoresistive Element Reducing Switching Current

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Solution Overview

Problem

Current magnetoresistive random access memory (MRAM) technologies face challenges in achieving high thermal disturbance resistance and reducing switching current while maintaining perpendicular magnetic anisotropy, as the damping constant increases with the spin pumping effect, and existing multilayer structures fail to achieve both low damping and high magnetoresistive ratios simultaneously.

Innovation Solution

A magnetoresistive element is designed with a first reference layer having perpendicular magnetic anisotropy and invariable magnetization, a recording layer with a stacked structure of alternately stacked magnetic and nonmagnetic layers, and an intermediate layer containing a nonmagnetic material, where the magnetic layers include a Co-Fe alloy with specific compositions and thicknesses to minimize damping and maximize magnetoresistive ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the magnetic anisotropic energy density is increased by increasing the film thickness or saturation magnetization of the magnetic layer, then thermal disturbance resistance is improved, but the spin-polarized current required for magnetization reversal increases

Engineering Contradiction:

Improvethermal disturbance resistanceVSAvoidspin-polarized current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The invention changes the magnetic anisotropy parameter from in-plane to perpendicular magnetization arrangement. This fundamental parameter change allows the magnetic moment to be oriented perpendicular to the film surface, enabling thermal stability without requiring increased film thickness or saturation magnetization, thus avoiding the penalty of higher switching currents.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention employs composite material structures including Co-Cr alloy materials with specific crystallographic orientations and multilayer configurations. These composite structures provide perpendicular magnetic anisotropy through interface effects and crystallographic engineering, achieving high thermal stability with low switching currents by leveraging material composition and structure rather than simply increasing thickness.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the aspect ratio of an MTJ element is increased to increase the magnetic anisotropic energy density, then thermal disturbance resistance is improved, but the cell area increases

Engineering Contradiction:

Improvethermal disturbance resistanceVSAvoidcell area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The invention changes the magnetization arrangement parameter from in-plane to perpendicular orientation. This parameter change enables the magnetic moment to align perpendicular to the film surface, providing high magnetic anisotropic energy density without requiring increased aspect ratio, thus maintaining small cell area while achieving high thermal stability.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If the crystal orientation is controlled such that the c-axis is parallel to a direction perpendicular to the film surface in a perpendicular magnetization arrangement, then the dispersion of the crystallographic axis is suppressed, but the magnetoresistance decreases or incoherent precession is induced

Engineering Contradiction:

Improvecrystallographic axis alignmentVSAvoidmagnetoresistance

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The invention changes the magnetization arrangement from in-plane to perpendicular orientation. This parameter change fundamentally alters how crystallographic alignment affects magnetoresistance. In perpendicular magnetization, the c-axis perpendicular to the film surface provides stable magnetic anisotropy without the dispersion problems of in-plane arrangements, and the magnetoresistance is maintained through proper interface engineering and material composition rather than being degraded by crystal orientation control.

Inventive Principle:

Principle #35Parameter changes

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 effectively reduces the damping constant and switching current density while maintaining high thermal disturbance resistance and magnetoresistive ratios, enabling efficient data storage and retrieval in MRAM devices.

Implementation Method 1

The giant magnetoresistive (GMR) effect or tunneling magnetoresistive (TMR) effect is applied to a magnetic head of the HDD. Both the GMR effect and TMR effect detect a magnetic field from a magnetic medium by using a resistance change caused by an angle the magnetization directions in two magnetic layers make with each other.

Methodology Applied

Scientific EffectGiant magnetoresistive (GMR) effect: Magnetoresistance

Implementation Method 2

Methodology Applied

Scientific EffectTunneling magnetoresistive (TMR) effect: Magnetoresistance

Implementation Method 3

magnetization reversal caused by a spin-polarized current has been theoretically predicted and experimentally confirmed, and an MRAM using a spin-polarized current has been proposed. This method can switch magnetization in a magnetic layer by only supplying a spin-polarized current to the magnetic layer.

Methodology Applied

Scientific EffectSpin transfer torque:

Implementation Method 4

An in-plane magnetization arrangement that has been principally studied so far generally uses the magnetic shape anisotropy. In this case, the magnetic anisotropy is secured by using the shape.

Methodology Applied

Scientific EffectMagnetic shape anisotropy: Anisotropy

Implementation Method 5

When using not the magnetic shape anisotropy but the magnetocrystalline anisotropy in the in-plane magnetization arrangement, if a material (e.g., a Co—Cr alloy material used in a hard disk medium) having a high magnetocrystalline anisotropic energy density is used

Methodology Applied

Scientific EffectMagnetocrystalline anisotropy: Anisotropy

Data Source

PatentUS8098514B2Magnetoresistive element and magnetic memory

Publication Date: 2012.01.17 KIOXIA CORP

AI summary

A magnetoresistive element includes a first reference layer having magnetic anisotropy perpendicular to a film surface, and an invariable magnetization, a recording layer having a stacked structure formed by alternately stacking magnetic layers and nonmagnetic layers, magnetic anisotropy perpendicular to a film surface, and a variable magnetization, and an intermediate layer provided between the first reference layer and the recording layer, and containing a nonmagnetic material. The magnetic layers include a first magnetic layer being in contact with the intermediate layer and a second magnetic layer being not in contact with the intermediate layer. The first magnetic layer contains an alloy containing cobalt (Co) and iron (Fe), and has a film thickness larger than that of the second magnetic layer.