Spintronic Accelerometer Using MTJ Free Layer Flexing

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current accelerometers, particularly piezoelectric displacement transducers, face challenges in achieving high density, miniaturization, and resistance to ElectroMagnetic Interference (EMI) while accurately measuring acceleration, especially in compact and strategic applications.

Innovation Solution

The development of a spintronic-based sensor device utilizing a magnetic tunnel junction (MTJ) element with a free layer, pinned layer, and tunnel barrier, where the free layer flexes towards or away from the tunnel barrier during acceleration, allowing processing circuitry to measure resistance and determine acceleration, offering enhanced resistance to EMI and compatibility with MRAM technology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If piezoelectric displacement transducers are used for acceleration detection, then measurement capability is provided, but device size and weight increase

Engineering Contradiction:

Improveacceleration detection capabilityVSAvoidaccelerometer weight

Core Design Contradiction:

Measurement precisionVSWeight of stationary object

Solution Approach 1:

The patent replaces piezoelectric mechanical transducers with a spintronic magnetic tunnel junction (MTJ) device that uses quantum tunneling and magnetoresistive effects. The MTJ element includes a free layer that flexes during acceleration, changing resistance to detect acceleration without requiring traditional piezoelectric mechanical structures, thereby reducing weight while maintaining measurement capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the detection parameter from piezoelectric voltage generation to magnetoresistive resistance change. The free layer of the MTJ element flexes during acceleration, altering the tunnel barrier width and thus the resistance, providing acceleration detection through electrical resistance measurement rather than voltage generation, enabling miniaturization

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If piezoelectric displacement transducers are used for acceleration detection, then measurement capability is provided, but resistance to ElectroMagnetic Interference (EMI) is reduced

Engineering Contradiction:

Improveacceleration detection capabilityVSAvoidElectroMagnetic Interference susceptibility

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention employs a composite MTJ structure with multiple functional layers including ferromagnetic layers, nonmagnetic spacer layers, and tunnel barrier layers. This composite spintronic structure inherently provides EMI resistance while enabling acceleration detection through the flexing free layer that modulates tunneling current based on acceleration-induced displacement

Inventive Principle:

Principle #40Composite materials

3Volume of moving object

If device miniaturization is pursued for higher density, then form factor is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improveaccelerometer volumeVSAvoidmanufacturing complexity

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

The patent combines the sensing element and readout functionality into a single integrated MTJ device structure. The free layer flexing mechanism is directly coupled to the tunnel barrier, eliminating the need for separate piezoelectric transducers and signal conditioning circuits, thereby reducing volume while simplifying manufacturing through monolithic integration

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention transitions from planar piezoelectric transducer geometry to a vertically stacked MTJ structure with multiple nanoscale layers. The free layer flexes in a direction that modulates the tunnel barrier width, utilizing the vertical dimension for sensing while maintaining a small footprint, enabling high-density integration without proportionally increasing manufacturing complexity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

This solution provides a higher density, more lightweight, and EMI-resistant acceleration detection, suitable for compact and strategic applications, with improved integration and customization capabilities, supporting compatibility with other sensing devices like gyros and pressure sensors.

Implementation Method 1

the free layer is adapted to flex towards or away from the tunnel barrier during acceleration

Methodology Applied

Scientific EffectFlexing: Elasticity

Implementation Method 2

The processing circuitry is configured to measure a resistance at the MTJ element and determine acceleration based on the resistance at the MTJ element

Methodology Applied

Scientific EffectMagnetic tunneling: Magnetoresistance

Data Source

PatentEP3623820B1Spintronic accelerometer

Publication Date: 2022.06.08 HONEYWELL INTERNATIONAL INC

Figure 1A
Figure 1B
Figure 1C

AI summary

A magnetic tunnel junction (MTJ) based sensor device includes a MTJ element and processing circuitry. The MTJ element includes a free layer, a pinned layer, and a tunnel barrier, the tunnel barrier being arranged between the free layer and the pinned layer. The free layer is adapted to flex away from the tunnel barrier during acceleration. The processing circuitry is configured to measure a resistance at the MTJ element and determine acceleration based on the resistance at the MTJ element.