Magnetic Tunnel Junction Sense Layer for Low-Anisotropy Field Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic field sensors with self-referenced magnetic tunnel junctions face angular errors due to finite magnetic anisotropy in the sense layer, which limits their accuracy, especially at low external magnetic field magnitudes, and increasing the sense layer thickness can lead to non-homogeneous magnetization and decreased performance.
Innovation Solution
A magnetic field sensor design with a sense ferromagnetic layer comprising a first and second ferromagnetic layer separated by a non-magnetic layer, where the second ferromagnetic layer is structured with multiple multilayer elements and a refractory metal non-magnetic layer, maintaining a thickness of 20 nm or less, to reduce anisotropy without increasing the sense layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the sense layer is increased to reduce magnetic anisotropy, then angular accuracy is improved, but non-homogeneous magnetization occurs in the plane of the sense layer
Solution Approach 1:
The sense layer is divided into multiple sub-layers (first sense layer, second sense layer, third sense layer) separated by non-magnetic layers. This segmentation allows each sub-layer to maintain uniform magnetization while the collective structure achieves reduced anisotropy, resolving the contradiction between thickness increase for accuracy and magnetization homogeneity.
Solution Approach 2:
The invention uses a composite structure combining ferromagnetic sense layers with non-magnetic spacer layers. This composite approach enables the sense layer to achieve low anisotropy through the combined effect of multiple thin layers rather than relying on a single thick layer, thus maintaining magnetization homogeneity while improving angular accuracy.
2Measurement precision
If the thickness of the sense layer is increased to reduce magnetic anisotropy, then angular accuracy is improved, but the minimum usable field of the magnetic sensor increases
Solution Approach 1:
By segmenting the sense layer into multiple thin sub-layers separated by non-magnetic layers, the invention achieves reduced magnetic anisotropy without increasing the overall thickness of individual ferromagnetic layers. This maintains the sensor's sensitivity to low magnetic fields while improving angular accuracy.
Solution Approach 2:
The invention changes the structural parameters of the sense layer from a single thick layer to multiple thin layers with specific thickness ratios. The first sense layer has thickness between 1-5 nm, the second sense layer has thickness between 1-3 nm, and the third sense layer has thickness between 1-5 nm, with non-magnetic layers in between. This parameter optimization reduces anisotropy while maintaining low-field sensitivity.
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 configuration reduces the anisotropy field, enhancing the angular accuracy of the sensor by minimizing energy differences between magnetization orientations, thereby improving low-field sensing without compromising performance.
Implementation Method 1
self-referenced magnetic tunnel junctions can be used to sense magnetic fields
Implementation Method 2
an external magnetic field aligns the sense magnetization more parallel or more antiparallel to the reference magnetization
Implementation Method 3
the sense layer has a preferred orientation of magnetization in this plane, which is the lowest-energy orientation
Data Source
AI summary
Magnetic field sensor for sensing a two-dimensional external magnetic field, including a magnetic tunnel junction including a reference layer having a fixed reference magnetization, a sense ferromagnetic layer having a sense magnetization, and a tunnel barrier layer between the sense and reference ferromagnetic layers; the sense ferromagnetic layer including a first sense ferromagnetic layer in contact with the tunnel barrier layer, a second sense ferromagnetic layer, and a first non-magnetic layer between the first and second sense ferromagnetic layers; the second sense ferromagnetic layer includes a plurality of multilayer element, each multilayer element including a second non-magnetic layer between two second ferromagnetic sense layers; and wherein the second sense ferromagnetic layer has a thickness equal or less than 12 nm.