Spin Polarized SEM Strain Analysis in Magnetic Materials

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Solution Overview

Problem

Current methods struggle to accurately measure and evaluate strain in iron and steel materials, particularly in magnetic materials, due to limitations in detecting small strain amounts and their distribution, which affects the performance and lifespan of structural and magnetic devices.

Innovation Solution

A scanning electron microscope equipped with a spin detector to measure secondary electron spin polarization, analyzing the width of regions where spin polarization changes to determine strain, allowing for precise evaluation of strain distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If EBSD method is used to measure strain, then lattice constant change can be detected, but detection precision is limited to about 0.01% strain amount

Engineering Contradiction:

Improvestrain detection precisionVSAvoiddetection limit

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent replaces the conventional EBSD mechanical/diffraction-based measurement system with a spin-polarized electron microscopy system. By utilizing spin polarization of secondary electrons instead of lattice diffraction patterns, the system achieves strain detection precision beyond the 0.01% limitation of EBSD, enabling detection of much smaller strain amounts through magnetic domain width measurements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Area of stationary object

If Kerr effect microscope is used to observe magnetic domains, then strain tendency in wide field of view can be determined, but quantitative evaluation of strain is difficult

Engineering Contradiction:

Improvefield of viewVSAvoidquantitative strain evaluation

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The spin-polarized scanning electron microscope combines the wide field of view capability of optical microscopy with the quantitative measurement precision of electron microscopy. The system maintains the ability to observe large areas while simultaneously providing precise quantitative strain evaluation through spin polarization measurements, eliminating the trade-off between observation area and measurement accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent changes the measurement parameter from optical contrast (qualitative) to spin polarization degree (quantitative). By measuring the spin polarization of secondary electrons, the system transforms the qualitative observation of magnetic domains into quantitative strain data, enabling precise strain evaluation while maintaining wide field of view capability.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If spin-polarized scanning electron microscope is used for magnetization mapping, then high resolution of 10 nm and three-dimensional detection is achieved, but application to strain analysis is limited

Engineering Contradiction:

Improvespatial resolutionVSAvoidapplication range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent extends the application range of the spin-polarized scanning electron microscope from solely magnetization mapping to include strain analysis. By establishing the correlation between spin polarization distribution and strain-induced magnetic domain structure changes, the system achieves multi-functionality, enabling both high-resolution magnetization characterization and quantitative strain measurement with the same apparatus.

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

Enables high-accuracy analysis of strain in magnetic materials, improving the evaluation of strain in iron and steel materials, enhancing the assessment of material performance and lifespan.

Implementation Method 1

a spin detector configured to measure spin polarization of a secondary electron emitted from a sample

Methodology Applied

Scientific EffectSpin polarization:

Implementation Method 2

when a surface of the sample is scanned with a primary electron beam and the spin polarization of the secondary electrons is sequentially measured

Methodology Applied

Scientific EffectElectron impact:

Data Source

PatentUS11170972B2Scanning electron microscope and method for analyzing secondary electron spin polarization

Publication Date: 2021.11.09 HITACHI HIGH TECH CORP

AI summary

A scanning electron microscope includes a spin detector configured to measure spin polarization of a secondary electron emitted from a sample, and an analysis device configured to analyze measurement data of the spin detector. The analysis device determines a width of a region where the secondary electron spin polarization locally changes in the measurement data. The analysis device further evaluates a strain in the sample based on the width of the region. With a configuration of the scanning electron microscope, it is possible to perform analysis of a strain in a magnetic material with high accuracy.