Magnetic Sensor Curie Temperature Ratio for Low Thermal Drift
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Solution Overview
Problem
Magnetic sensors using magnetoresistance effect elements are sensitive to environmental temperature, affecting their output characteristics due to the temperature-dependent magnetic characteristics of the magnet film on the lateral side of the free layer.
Innovation Solution
A magnetic sensor design where at least one magnet film is disposed on the lateral side of the free layer, applying a bias magnetic field, with a controlled Curie temperature relationship of 0.7≤TC_HM/TC_FL≤1.05 between the Curie temperature of the magnet film and the free layer, minimizing temperature sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnet film is provided on the lateral side of a free layer to make the magnetization direction uniform, then the magnetic sensor achieves higher output and sensitivity, but the output characteristic becomes more sensitive to environmental temperature
Solution Approach 1:
The patent changes the Curie temperature parameter of the magnet film by adjusting its composition (adding Pt, Pd, or Ir to CoFeB) to achieve a specific ratio range (0.7≤TC_HM/TC_FL≤1.05) with the free layer's Curie temperature. This parameter optimization makes the magnet film's magnetic characteristics less sensitive to environmental temperature changes, thereby reducing the temperature sensitivity of the overall sensor output while maintaining high sensitivity through the lateral bias field configuration
2Reliability
If the Curie temperature of the magnet film is increased to reduce temperature sensitivity, then the magnetic characteristics become more stable, but the device complexity increases due to composition control requirements
Solution Approach 1:
The patent uses composite material design by combining CoFeB with Pt, Pd, or Ir elements to create a magnet film with optimized Curie temperature. This composite approach achieves the desired temperature stability through material composition rather than complex structural designs, maintaining reliability while managing device complexity through straightforward compositional control during fabrication
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 design reduces the sensitivity of the magnetic sensor's output characteristic to environmental temperature, maintaining accuracy across a wide temperature range while optimizing the Curie temperature ratio for minimal offset change.
Implementation Method 1
at least one magnet film that is disposed on a lateral side of the free layer and that applies a bias magnetic field to the free layer
Implementation Method 2
a spacer layer that is located between the pinned layer and the free layer and that exhibits a magnetoresistance effect
Implementation Method 3
The relationship of 0.7≤TC_HM/TC_FL≤1.05 is satisfied, where TC_HM is the Curie temperature of the magnet film, and TC_FL is the Curie temperature of the free layer
Data Source
AI summary
A magnetic sensor whose output characteristic is less sensitive to the environmental temperature is provided. Magnetic sensor 1 has free layer 24 whose magnetization direction changes in response to an external magnetic field, pinned layer 22 whose magnetization direction is fixed with respect to the external magnetic field, spacer layer 23 that is located between pinned layer 22 and free layer 24 and that exhibits a magnetoresistance effect, and at least one magnet film 25 that is disposed on a lateral side of free layer 24 and that applies a bias magnetic field to free layer 24. A relationship of 0.7 ≤TC_HM/TC_FL≤1.05 is satisfied, where TC_HM is Curie temperature of the magnet film, and TC_FL is Curie temperature of the free layer.