Spintronics: Fundamentals and Applications

✍ Scribed by Puja Dey, Jitendra Nath Roy

• Publisher: Springer
• Year: 2021
• Tongue: English
• Leaves: 287
• Category: Library

✦ Synopsis

This book highlights the overview of Spintronics, including What is Spintronics ?; Why Do We Need Spintronics ?; Comparative merit-demerit of Spintronics and Electronics ; Research Efforts put on Spintronics ; Quantum Mechanics of Spin; Dynamics of magnetic moments : Landau-Lifshitz-Gilbert Equation; Spin-Dependent Band Gap in Ferromagnetic Materials; Functionality of ‘Spin’ in Spintronics; Different Branches of Spintronics etc. Some important notions on basic elements of Spintronics are discussed here, such as – Spin Polarization, Spin Filter Effect, Spin Generation and Injection, Spin Accumulation, Different kinds of Spin Relaxation Phenomena, Spin Valve, Spin Extraction, Spin Hall Effect, Spin Seebeck Effect, Spin Current Measurement Mechanism, Magnetoresistance and its different kinds etc. Concept of Giant Magnetoresistance (GMR), different types of GMR, qualitative and quantitative explanation of GMR employing Resistor Network Theory are presented here. Tunnelling Magnetoresistance (TMR), Magnetic Junctions, Effect of various parameters on TMR, Measurement of spin relaxation length and time in the spacer layer are covered here. This book highlights the concept of Spin Transfer Torque (STT), STT in Ferromagnetic Layer Structures, STT driven Magnetization Dynamics, STT in Magnetic Multilayer Nanopillar etc. This book also sheds light on Magnetic Domain Wall (MDW) Motion, Ratchet Effect in MDW motion, MDW motion velocity measurements, Current-driven MDW motion, etc. The book deals with the emerging field of spintronics, i.e., Opto-spintronics. Special emphasis is given on ultrafast optical controlling of magnetic states of antiferromagnet, Spin-photon interaction, Faraday Effect, Inverse Faraday Effect and outline of different all-optical spintronic switching. One more promising branch i.e., Terahertz Spintronics is also covered. Principle of operation of spintronic terahertz emitter, choice of materials, terahertz writing of an antiferromagnetic magnetic memory device is discussed. Brief introduction of Semiconductor spintronics is presented that includes dilute magnetic semiconductor, feromagnetic semiconductor, spin polarized semiconductor devices, three terminal spintronic devices, Spin transistor, Spin-LED, and Spin-Laser. This book also emphasizes on several modern spintronics devices that includes GMR Read Head of Modern Hard Disk Drive, MRAM, Position Sensor, Biosensor, Magnetic Field sensor, Three Terminal Magnetic Memory Devices, Spin FET, Race Track Memory and Quantum Computing.

✦ Table of Contents

Preface
Aim and Purpose
Organization of the Book
Target Audience
Request Feedback
Acknowledgements
Contents
About the Authors
1 An Overview of Spintronics
1.1 Introduction
1.1.1 What Is Spintronics?
1.1.2 Why Do We Need Spintronics?
1.2 Comparative Merit–Demerit of Spintronics and Electronics
1.2.1 What Are the Disadvantages of Electronics?
1.2.2 What Are then the Advantages of Spintronics Over Electronics?
1.2.3 Advantages of Spintronics
1.3 Research Efforts Put on Spintronics
1.4 Evolution of Spintronics
1.4.1 History of Spin
1.5 Quantum Mechanics of Spin
1.5.1 Pauli Spin Matrices
1.5.2 Eigenvectors of the Pauli Matrices: SPINORS
1.6 Dynamics of Magnetic Moments: Landau-Lifshitz-Gilbert Equation
1.7 Spin-Dependent Band Gap in Ferromagnetic Materials
1.8 Functionality of ‘Spin’ in Spintronics
1.8.1 Basic Principle of Working of All Spintronic Devices (Simple Scheme)
1.9 Different Branches of Spintronics
1.9.1 Branching Based on Choice of Materials
1.9.2 Branching Based on Magnetic Manipulation
1.10 Applications
1.10.1 Presently, Do We Have Any Spintronics-Powered Products?
1.10.2 Future Scope of Work
1.11 Conclusions
1.12 Exercises
References
2 Basic Elements of Spintronics
2.1 Spin Polarization
2.2 Spin Filter Effect
2.2.1 What Is Spin Filter Effect?
2.2.2 Physical Interpretation of Spin Asymmetry ‘A’
2.2.3 Spin Detection Efficiency
2.3 Spin Generation and Injection
2.3.1 What Is Spin Injection?
2.3.2 Transport Method
2.3.3 Knowledge of Some Essential Parameters of Injector Ferromagnet
2.3.4 Sustainability of Spin Polarization in Paramagnet
2.3.5 Discussion of Spin Injection Process in Two Cases
2.4 Spin Accumulation
2.4.1 What Is Spin Accumulation?
2.4.2 Estimation of Spin Accumulation Length by a Simple Method
2.5 Spin Relaxation
2.5.1 What Is Spin Relaxation?
2.5.2 What Is Spin–Orbit Interaction?
2.5.3 Spin Relaxation Process
2.6 Elliott–Yafet Mechanism
2.6.1 What Is the Prerequisite Condition for Elliott–Yafet Mechanism?
2.6.2 Elliott–Yafet Mode of Spin Scattering Mechanism
2.6.3 Where Does the Elliott–Yafet Mechanism of Spin Scattering Occur?
2.7 D’yakonov-Perel’ Mechanism
2.7.1 What Is the Prerequisite Condition for D’yakonov-Perel’ Mechanism?
2.7.2 D’yakonov-Perel’ Mode of Spin Scattering Mechanism
2.7.3 Is Frequent Momentum Scattering Actually Be Beneficial for Spin Longevity!!
2.7.4 Where Does D’yakonov-Perel’ Mechanism Occur?
2.8 Bir-Aronov-Pikus Mechanism
2.8.1 Where Does the Bir-Aronov-Pikus Mechanism of Spin Scattering Occur?
2.9 Hyperfine Interaction
2.10 Spin Valve
2.10.1 What Is Spin Valve Device?
2.10.2 Operation of Spin Valve
2.10.3 Description of Spin Valve Device Experiments
2.10.4 Physical Description of Spin Valve Effect
2.11 Spin Extraction
2.12 Field- and Heat-Driven Spintronics Effect
2.12.1 Field-Driven Hall Effect
2.12.2 Heat-Driven Seebeck Effect
2.13 Spin Current Measurement Mechanism
2.14 Conclusions
2.15 Exercises
References
3 Giant Magnetoresistance (GMR)
3.1 Introduction to Magnetoresistance
3.2 Different Kinds of MR
3.2.1 Ordinary Magnetoresistance
3.2.2 Magnetoresistance of Ferromagnetic Transition Metals
3.2.3 Anisotropic Magnetoresistance (AMR) of Ferromagnetic Transition Metals
3.3 Introduction on Giant Magnetoresistance (GMR)
3.3.1 What Is GMR?
3.3.2 How Is GMR Effect?
3.4 Types of GMR
3.4.1 Multilayer GMR
3.4.2 Spin Valve GMR
3.4.3 Pseudo-spin Valve GMR
3.4.4 Granular GMR
3.5 Physical Origin of GMR: Qualitative Explanation
3.5.1 What Is Spin-Dependent and Spin-Flip Scattering of Electrons in Multilayers?
3.5.2 How Does Mott Model Describe GMR?
3.5.3 Explanation of Negative MR of Ferromagnetic Transition Metal, Considering Spin Scattering Mechanisms
3.5.4 Explanation of GMR by Mott Model
3.6 Quantitative Explanation of GMR
3.7 Magnetoresistance Theory
3.7.1 Resistor Network Theory of GMR
3.7.2 Calculation for Ferromagnetic Configuration
3.7.3 Calculation for Antiferromagnetic Configuration
3.8 Conclusions
3.9 Exercises
References
4 Tunnelling Magnetoresistance (TMR)
4.1 Introduction on Tunnelling Magnetoresistance
4.1.1 Introductory Note
4.1.2 What Is Magnetic Tunnel Junction (MTJ)?
4.1.3 What Is Tunnelling Magnetoresistance (TMR)?
4.2 Magnetic Junctions
4.2.1 Tunnel-Type Junction
4.2.2 Contact Type Junction
4.3 Physical Explanation
4.3.1 Background
4.3.2 Spin-Dependent Conductance of Charge Carriers
4.3.3 Tunnelling Process
4.3.4 The Jullière Formula
4.3.5 Simple Description of Tunnelling Phenomenon
4.4 Effect of Various Parameters on Tunnel Magnetoresistance
4.4.1 Effect of Paramagnetic Impurities at the Interface on Magnetoresistance
4.4.2 Effect of Magnetic Excitations on the MR
4.4.3 Effect of Magnetic Properties of the Interface on MR
4.4.4 Effect of Charging in Granular Systems on MR
4.5 Measurement of Spin Relaxation Length and Time in the Spacer Layer
4.6 Conclusions
4.7 Exercises
References
5 Spin-Transfer Torque
5.1 Introduction on Spin-Transfer Torque
5.1.1 What Is Spin-Transfer Torque (STT)?
5.2 Spin-Transfer Torque in Ferromagnetic Layer Structures
5.2.1 Single Ferromagnetic (FM) Layer
5.2.2 Double Ferromagnetic (FM) Layers
5.3 Spin-Transfer Torque (STT)-Driven Magnetization Dynamics
5.3.1 Magnetization Dynamics in Absence of STT
5.3.2 Magnetization Dynamics in Presence of STT
5.4 Experimental Results
5.4.1 Point Contact Device
5.4.2 Multilayer Nanopillar
5.5 Spin-Transfer Torque in Magnetic Multilayer Nanopillar
5.5.1 Spin-Transfer Torque Exerted in Metallic Junctions
5.5.2 Spin-Transfer Torque Exerted in Magnetic Tunnel Junctions (MTJs)
5.6 Possible Applications of Spin-Transfer Torques
5.6.1 Magnetic Random Access Memory
5.6.2 Spin-Transfer Torque-Driven Microwave Sources and Oscillators
5.7 Conclusions
5.8 Exercises
References
6 Magnetic Domain Wall Motion
6.1 Introduction on Magnetic Domain Wall Motion
6.1.1 What Is Magnetic Domain Wall?
6.1.2 Why Do Domains Exist?
6.1.3 What Is Domain Wall Width?
6.1.4 Why Small Particles Are Always Mono-domain?
6.2 Magnetic Domain Wall Motion in Spintronics
6.2.1 Detection of Domain-Wall (DW) Propagation
6.3 Ratchet Effect in Magnetic Domain Wall Motion
6.3.1 What Is Rachet Effect?
6.3.2 Rachet Effect in Magnetic Domain Wall Motion
6.3.3 Rachet Effect in Spintronics
6.4 Domain Wall Motion Velocity Measurements
6.5 Current-Driven Domain Wall Motion
6.5.1 What Will Happen if Electric Current Flow Through This Domain Wall?
6.5.2 Applications of Current-Driven Domain Wall Motion
6.6 Conclusions
6.7 Exercises
References
7 Opto-spintronics
7.1 Introduction: What Is Opto-spintronics?
7.2 What Is so Special About Femtosecond Laser?
7.3 Issues to Be Considered: Why Do We Need Optical Manipulation?
7.4 Laser Pulse and Its Impact on a Magnetic System
7.4.1 Thermal Effects
7.4.2 Non-thermal Effects
7.5 Interaction of Photons and Spins
7.6 Experimental Techniques
7.6.1 Pump and Probe Method
7.6.2 Optical Probe
7.6.3 Far-Infrared (F-IR) Probe
7.6.4 X-ray Probe
7.7 Demagnetization of Metallic Ferromagnets: 3TM Model
7.8 Demagnetization of Ferromagnetic Semiconductor: GaMnAs
7.9 Antiferromagnetic Opto-spintronics
7.9.1 Brief History of the Emergence of Antiferromagnetic Spintronics
7.9.2 Probing and Optical Manipulation of Antiferromagnets
7.10 All-Optical Spintronic Switching
7.11 Conclusion
7.12 Exercises
References
8 Terahertz Spintronics
8.1 Introduction
8.2 What Is Terahertz Radiation?
8.3 Why Terahertz Radiation Is so Important?
8.4 Why Do We Need Terahertz Spintronics?
8.5 Spintronic Terahertz Emitter (STE)
8.5.1 Metallic Spintronic THz Emitter (MSTE)
8.5.2 THz Emitter with Magnetic Insulator (F)/Non-magnetic Metal (N) Layer
8.5.3 Comparison Between Metallic Magnet (Fe) and Non-metallic Magnet (YIG)
8.5.4 Terahertz Emission by Complex Magnetic Compounds
8.6 Terahertz Writing
8.7 Conclusion
8.8 Exercises
References
9 Semiconductor Spintronics
9.1 Introduction
9.2 Issues to Be Considered
9.3 Materials, Structures and Spin Injection
9.4 Spin-Polarized Semiconductor Devices
9.4.1 Three Terminal Spintronic Devices
9.4.2 Spin-Polarized Field-Effect Transistors (Spin FET)
9.4.3 Spin Light Emitting Diode (Spin LED)
9.4.4 Spin-Polarized Resonant Tunnelling Diodes (Spin RTD)
9.4.5 Spin Laser
9.5 Conclusion
9.6 Exercises
References
10 Spintronics Applications
10.1 Overview
10.2 Historical Advancement and Development of Spintronic Devices
10.3 Read Head in Magnetic Data Storage
10.3.1 Application of GMR Effect
10.3.2 Role of GMR in Magnetic Data Storage
10.3.3 Internal Structure of a Magnetic Hard Disk
10.3.4 Operation of Magnetoresistance Read Heads
10.3.5 Evolution of Magnetoresistance Read Head Sensor
10.3.6 Spin Valve Sensors
10.3.7 Some Important Features of Spin-Valve GMR Read Head Applications
10.4 Magnetic Random Access Memories (MRAM)
10.4.1 Application Based on Spin-Tunnel Junctions
10.4.2 Background
10.4.3 Why MRAM Should Be Used?
10.4.4 About MTJ-Based Magnetic Random Access Memories (MRAM)
10.4.5 Basic Cell Operation
10.4.6 Applications of M-RAM
10.5 Spin Transfer Torque (STT)—MRAM
10.5.1 Introduction
10.5.2 What Is STT-MRAM?
10.5.3 What Is Perpendicular STT-MRAM?
10.5.4 Application of STT-MRAM
10.5.5 The Latest STT-MRAM
10.6 Spintronics Sensors
10.6.1 Anisotropic Magnetoresistance Sensor
10.6.2 Some GMR-Based Sensors Applications
10.6.3 Some Magnetic Tunnel Junction-Based TMR Sensor Applications
10.7 Spin FET
10.7.1 Working of Spin FET
10.7.2 Advantages of Spin FET
10.8 Racetrack Memory
10.8.1 What Is Racetrack Memory?
10.8.2 Advantages and Disadvantages
10.8.3 How Does it Work?
10.9 Quantum Computing
10.9.1 Bloch Sphere Representation
10.9.2 Quantum Properties and Computing
10.10 Conclusions
10.11 Exercises
References
Subject Index