Wurft, Tobias: Investigation of the Magnetic Vortex State for Spin-Valve Sensors. 2018
Inhalt
- Table of Contents
- Symbols and Acronyms
- 1 Introduction
- 1.1 Magnetoresistive Sensors in Automotive Applications - Example Wheel Speed Sensing
- 1.2 Motivation and Outline
- 2 The Magnetic Vortex
- 2.1 Properties of the Magnetic Vortex
- 2.2 Theoretical Background and Fields of Research
- 2.3 Energy Analysis of the Vortex State
- 3 Methodology
- 3.1 Implementation of the Vortex Sensor Concept
- 3.1.1 Tunnel Magnetoresistance
- 3.1.2 Tunneling Magnetoresistance Spin-Valve
- 3.1.3 Stack and Layout Variants
- 3.1.4 Device Characteristics
- 3.2 Experimental Methods
- 3.3 Simulations Methodology
- 4 Experimental Results - Intrinsic Factors
- 4.1 Disk Dimensions - Diameter and Thickness
- 4.1.1 Fields of Research
- 4.1.2 Lateral Size and Aspect Ratio
- 4.1.3 Collapse and Estimated Stray Field of the Saturated State
- 4.1.4 Stray Field Energy of the Saturated State
- 4.1.5 Thickness-Dependent Nucleation Modes - Simulations
- 4.1.6 Thickness-Dependent Nucleation Modes - Experiment
- 4.1.7 Nucleation Modes and the Influence of the Diameter
- 4.1.8 Symmetry Breaking of the Vortex Core
- 4.2 Material and Process
- 4.2.1 Saturation Magnetization
- 4.2.2 Exchange Stiffness
- 4.2.3 Magneto-Crystalline Anisotropy
- 4.2.4 Magneto-Crystalline Anisotropy and Direction of Rotation of the Vortex State
- 4.2.5 Magneto-Crystalline Anisotropy and Increased Stability of the Double Vortex State
- 4.2.6 Magneto-Crystalline Anisotropy and Crossed Hysteresis
- 4.2.7 Magnetically Disturbed Edge
- 4.2.8 Sloped Edge
- 4.2.9 Edge Effects in Combination with Magneto-Crystalline Anisotropy
- 4.2.10 Electrically Inactive Edge
- 4.2.11 Edge Shape - Discretization and Roughness
- 5 Experimental Results - Extrinsic Factors
- 5.1 Processing of Changes of Critical Fields
- 5.2 Temperature
- 5.2.1 Initial Expectations
- 5.2.2 Types of Temperature-Induced Nucleation Field Shifts
- 5.2.3 Nucleation Modes and Temperature-Induced Nucleation Field Shifts
- 5.2.4 Magneto-Crystalline Anisotropy and Temperature-Induced Nucleation Field Shifts
- 5.2.5 Temperature-Induced Annihilation Field Shifts
- 5.2.6 Estimation of the Temperature-Induced Reduction of the Saturation Magnetization and Thermally Assisted Barrier Jumps
- 5.2.7 Summary
- 5.3 Bias Fields
- 6 Summary and Outlook
- List of Publications
- Bibliography