Diluted Magnetic Free Layer for STT-MRAM Switching

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Solution Overview

Problem

Conventional STT-MRAMs require high switching currents, which can lead to thermal instability and hinder performance improvements, necessitating a method to reduce switching current while maintaining thermal stability and exchange stiffness.

Innovation Solution

Incorporating a diluted magnetic layer with a nonmagnetic material alloyed into a magnetic material within the free layer of magnetic junctions, which maintains exchange stiffness and increases thickness, allowing for reduced switching currents and improved performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional free layer is used in STT-MRAM, then the magnetic junction can be switched by driving current perpendicular to plane, but high switching currents are required which lead to thermal instability

Engineering Contradiction:

Improvethermal stabilityVSAvoidswitching current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the composition parameter of the free layer by introducing a diluted magnetic layer containing both magnetic atoms (Co, Fe) and nonmagnetic atoms (Al, Ga, In). This compositional parameter change reduces the saturation magnetization while maintaining perpendicular magnetic anisotropy, thereby reducing the switching current requirement and improving thermal stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite magnetic layer by alloying magnetic materials with nonmagnetic materials in a diluted configuration. This composite structure combines the beneficial properties of both components: the magnetic atoms provide the necessary magnetic moment while the nonmagnetic atoms reduce the overall saturation magnetization and enhance thermal stability

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If the free layer thickness is increased to improve switching performance, then switching current can be reduced, but exchange stiffness is reduced which harms thermal stability

Engineering Contradiction:

Improveswitching currentVSAvoidexchange stiffness

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent changes the concentration parameter of magnetic atoms in the diluted magnetic layer. By optimizing the ratio of magnetic to nonmagnetic atoms, the patent achieves a balance where the reduced saturation magnetization lowers switching current while the maintained exchange stiffness preserves thermal stability. The specific composition range (e.g., 30-70 at% magnetic atoms) is critical for achieving this balance

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 diluted magnetic layer reduces saturation magnetization while preserving exchange stiffness, enabling lower switching currents and enhanced switching speed and thermal stability in magnetic devices.

Implementation Method 1

The SO active layer(s) carry a current in-plane and exert a SO torque on the free layer due to the current passing through the SO active layer(s)

Methodology Applied

Scientific EffectSpin-orbit torque:

Implementation Method 2

The diluted magnetic layer has an exchange stiffness that is at least eighty percent of an exchange stiffness for the magnetic material(s)

Methodology Applied

Scientific EffectExchange stiffness:

Data Source

PatentUS10205092B2Method and system for providing a diluted free layer magnetic junction usable in spin transfer or spin-orbit torque applications

Publication Date: 2019.02.12 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetic device and method for providing the magnetic device are described. The magnetic device includes magnetic junctions and spin-orbit interaction (SO) active layer(s). The magnetic junction includes free and pinned layers separated by a nonmagnetic spacer layer. The free layer has a free layer perpendicular magnetic anisotropy (PMA) energy greater than a free layer out-of-plane demagnetization energy. The free layer also includes a diluted magnetic layer that has a PMA greater than its out-of-plane demagnetization energy. The diluted magnetic layer includes magnetic material(s) and nonmagnetic material(s) and has an exchange stiffness that is at least eighty percent of an exchange stiffness for the magnetic material(s). The SO active layer(s) are adjacent to the free layer. The SO active layer(s) carry a current in-plane and exert a SO torque on the free layer due to the current. The free layer is switchable between stable magnetic states using the SO torque.