Nanometer Magnetic Multilayer Film for High-Accuracy Temperature Sensing
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Solution Overview
Problem
Existing temperature sensors face issues such as large size, high cost, poor linearity, low measurement accuracy, and limited range, making them unsuitable for various applications, particularly in aerospace and industrial settings where high accuracy and miniaturization are required.
Innovation Solution
A nanometer magnetic multilayer film for magnetic tunnel junction-based temperature sensors is developed, featuring three types of structures: one with indirect or direct pinning, synthetic ferromagnetic or anti-ferromagnetic structures, and another with perpendicular magnetic layers, optimized through specific annealing processes to achieve linear resistance variation with temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature sensors (thermocouple, thermistor, platinum resistor) are used, then temperature measurement function is achieved, but they suffer from large size, high cost, poor linearity, low measurement accuracy, or limited measurement range
Solution Approach 1:
The patent replaces conventional mechanical/chemical temperature sensing mechanisms with a magnetic tunnel junction (MTJ) device that utilizes quantum tunneling magnetoresistance effect. The MTJ device measures temperature through resistance changes in the anti-parallel state without requiring complex mechanical structures or chemical materials like thermocouples or platinum resistors, thereby achieving high measurement accuracy with simplified device structure
Solution Approach 2:
The patent exploits the temperature-dependent resistance characteristic of the MTJ device in the anti-parallel state. By monitoring resistance changes as a function of temperature, the device achieves high measurement accuracy. The linear relationship between resistance and temperature in the anti-parallel state provides excellent measurement precision without the limitations of conventional sensors
2Measurement precision
If thermocouple temperature sensor is used, then temperature measurement is achieved, but it requires cold-end temperature compensation circuit and has large size
Solution Approach 1:
The patent extracts the temperature sensing function from complex external compensation circuits and integrates it directly into the MTJ device structure. The MTJ device inherently provides temperature-dependent resistance changes that can be directly measured without requiring separate cold-end compensation circuits, thereby miniaturizing the overall sensor system while maintaining high measurement accuracy
Solution Approach 2:
The MTJ device serves multiple functions: it acts as both the temperature sensing element and the signal generation source. The device's resistance in the anti-parallel state naturally varies with temperature, eliminating the need for separate compensation mechanisms and reducing the overall sensor size while maintaining measurement precision
3Measurement precision
If platinum resistor temperature sensor is used, then temperature measurement is achieved, but it has self-heating problem and high cost due to precious metal
Solution Approach 1:
The patent replaces expensive precious metals (platinum) with ferromagnetic materials and insulating barriers that form the MTJ structure. This substitution dramatically reduces material cost while maintaining high measurement accuracy. The MTJ device achieves comparable or superior performance without the self-heating problems associated with platinum resistors, as it operates at lower power levels
Solution Approach 2:
The patent replaces the resistive heating mechanism of platinum resistors with a magnetic tunneling mechanism. The MTJ device measures temperature through quantum tunneling effects rather than Joule heating, thereby eliminating self-heating problems and reducing power consumption while maintaining high measurement accuracy
4Ease of manufacture
If thermistor temperature sensor is used, then temperature measurement is achieved, but it has poor linearity and relatively low measurement accuracy
Solution Approach 1:
The patent replaces the semiconductor-based resistive mechanism of thermistors with a magnetic tunneling mechanism. The MTJ device exhibits superior linearity between resistance and temperature in the anti-parallel state, achieving both high measurement accuracy and ease of manufacture through standard thin-film deposition techniques
Solution Approach 2:
The patent uses composite material structures in the MTJ device, combining ferromagnetic layers with insulating barriers (such as MgO). This composite structure enables excellent linearity and high measurement accuracy while maintaining compatibility with standard manufacturing processes, overcoming the limitations of single-material thermistor devices
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 enables the creation of high-accuracy, low-power, miniaturized temperature sensors with excellent linearity and integration capabilities, suitable for a wide range of applications including aerospace and industrial use.
Implementation Method 1
the magnetic tunnel junction has a significantly different resistance in the parallel state than in the anti-parallel state, which is also called as Tunneling MagnetoResistance (TMR) effect
Implementation Method 2
a phenomenon is observed in the magnetic tunnel junctions that its resistance in the anti-parallel state varies linearly with respect to temperature
Implementation Method 3
A first type is manufactured with a synthetic ferromagnetic or anti-ferromagnetic structure and a pinning structure using a one-time annealing process
Data Source
AI summary
A magnetic multilayer film for a temperature sensor is disclosed. The magnetic multilayer film comprises: a bottom magnetic composite layer provided on a substrate, the bottom magnetic composite layer having a direct pinning structure, an indirect pinning structure, a synthetic ferromagnetic structure, or a synthetic anti-ferromagnetic structure; a spacer layer provided on the bottom magnetic composite layer; and a top magnetic composite layer provided on the spacer layer, the top magnetic composite layer having the direct pinning structure, the indirect pinning structure, the synthetic ferromagnetic structure, or the synthetic anti-ferromagnetic structure, wherein a ferromagnetic layer of the bottom magnetic composite layer closest to the spacer layer has a magnetic moment anti-parallel with that of a ferromagnetic layer of the top magnetic composite layer closest to the spacer layer.