Magnetic Sensor Element With Indirect Exchange for Wider Dynamic Range
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Solution Overview
Problem
The upper limit of magnetic field intensity measurable by existing magnetic detection elements is limited, resulting in a insufficient dynamic range for detecting small magnetic field variations.
Innovation Solution
A magnetic sensor element comprising a pinned layer, a first non-magnetic layer, a first magnetic layer, and a free layer, where the pinned layer and first magnetic layer are coupled by indirect exchange interaction, allowing for increased sensitivity to external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spin-valve giant magnetic resistance (GMR) element is used as a magnetic detection element, then hysteresis is reduced under a bias magnetic field, but the upper limit of measurable magnetic field intensity is limited to the anisotropic magnetic field intensity (Hk) of the free layer, resulting in insufficient dynamic range
Solution Approach 1:
The magnetic detection element is divided into multiple functional layers: a pinned layer with fixed magnetization direction, a first magnetic layer with in-plane magnetization, and a free layer with perpendicular magnetization. Each layer serves a specific function, allowing the element to detect magnetic fields beyond the limited range of conventional single-layer GMR elements.
Solution Approach 2:
The invention transitions from conventional in-plane magnetization detection to perpendicular magnetization detection by orienting the magnetization direction of the free layer perpendicular to the film plane. This dimensional change enables detection of much stronger magnetic fields, expanding the dynamic range from limited Hk values to fields exceeding 1 T.
2Measurement precision
If a bias magnetic field is applied to increase magnetic field variation detection, then sensitivity to small magnetic field variations is improved, but the intensity of the bias magnetic field is about 1000 times greater than the magnetic field variation to be detected
Solution Approach 1:
The invention changes the magnetization orientation parameter from in-plane to perpendicular for the free layer, which fundamentally alters the magnetic detection characteristics. This parameter change enables the use of much weaker bias magnetic fields while maintaining high sensitivity, as the perpendicular magnetization configuration provides enhanced magnetic field responsiveness.
3Adaptability or versatility
If the free layer has perpendicular magnetization direction, then the upper limit of measurable magnetic field intensity exceeds 1 T, but the device complexity increases with multiple layers and indirect exchange interaction
Solution Approach 1:
A nonmagnetic layer is introduced as an intermediary between the pinned layer and the first magnetic layer. This intermediary layer enables indirect exchange interaction, which couples the magnetization directions of adjacent layers without requiring direct contact. This approach simplifies the overall structure compared to direct exchange coupling while achieving the desired perpendicular magnetization configuration.
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 dynamic range of the magnetic sensor element is significantly enhanced, enabling accurate detection of small magnetic field variations with improved sensitivity and reduced hysteresis.
Implementation Method 1
The pinned layer and the first magnetic layer are coupled by indirect exchange interaction
Implementation Method 2
a magnetic detection element (magnetic sensor element) described in Japanese Patent Laying-Open No. 2006-019383 (PTL 1) is a spin-valve giant magnetic resistance (GMR) element
Implementation Method 3
a magnet for applying a bias magnetic field to the magnetic sensor element
Data Source
AI summary
A magnetic sensor element includes a pinned layer, a first non-magnetic layer, a first magnetic layer, and a free layer. The pinned layer has a fixed magnetization direction. The first non-magnetic layer is laminated on the pinned layer. The first magnetic layer holds the first non-magnetic layer with the pinned layer. The free layer is disposed along a lamination direction in which the first non-magnetic layer is laminated on the pinned layer. Each of the first magnetic layer and the free layer has a magnetization direction more easily changed by an external magnetic field than that of the pinned layer. The pinned layer and the first magnetic layer are coupled by indirect exchange interaction.