Edited byKaiyou Wang is Director of State Key Laboratory of Superlattices & Microstructure, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China. Meiyin Yang is Professor at the Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing, China. Jun Luo is Professor at the Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing, China. Series Editors Arthur Willoughby University of Southampton, Southampton, UK Peter Capper Ex-Leonardo M. W. Ltd, Southampton, UK Safa Kasap University of Saskatchewan, Saskatoon, Canada

• List of Contributors xiSeries Preface xiiiPreface xv1 Introduction 1Kaiyou Wang2 Giant Magnetoresistance (GMR) Materials and Devices for Biomedical and Industrial Applications 3Kai Wu, Diqing Su, Renata Saha, and Jian-Ping Wang2.1 Introduction 32.2 Giant Magnetoresistance (GMR) Effect 42.3 Different Types of GMR Sensors 72.3.1 Rigid GMR Sensors 72.3.1.1 Long-strip GMR Sensors 72.3.1.2 Large-area GMR Sensors 82.3.2 Flexible GMR Sensors 92.3.3 Printable GMR Sensors 112.3.4 Granular GMR Sensors (Thin Film- and Solution-based) 112.4 GMR Sensors: Surface Modification and Auxiliary Tools 122.4.1 GMR Sensor Surface Modification for Biomedical Applications 122.4.2 Integration of a Magnetic Flux Concentrator (MFC) 142.4.2.1 Superconducting MFC 142.4.2.2 Soft-ferromagnetic Material-based MFC 142.4.3 Integration of Microfluidic Channels 162.5 GMR-based Biomedical Applications 162.5.1 GMR-based Immunoassays 162.5.1.1 Wash-free and Non-wash-free Immunoassays 172.5.1.2 Different Immunoassay Methods 172.5.1.3 GMR for Disease Diagnosis 192.5.1.4 GMR-based Point-of-Care (POC) Devices 242.5.2 GMR-based Genotyping 252.5.3 GMR-based Bio-magnetic Field Recording 282.5.4 GMR-based Food and Drug Safety Supervision 322.6 GMR-based Industrial Applications 342.6.1 GMR for Position Sensing 342.6.2 GMR for Current Sensing 352.6.3 GMR for Material Defect Inspection 372.7 Conclusions and Outlook 39References 403 Tunneling Magnetoresistance (TMR) Materials and Devices for Magnetic Sensors 51Zitong Zhou, Kun Zhang, and Qunwen Leng3.1 Principle of Tunneling Magnetoresistance Effect 523.1.1 Tunneling Process 523.1.2 Spin-dependent Tunneling Process 533.1.3 The Julliére Model 543.1.4 Typical Structure of the Magnetic Sensing Unit 563.2 Material and Process 563.2.1 TMR Barrier Materials 563.2.2 Ferromagnetic Layers in TMR 593.2.3 TMR Film Stack 613.2.4 Perpendicular Magnetic Anisotropy (PMA) in TMR 653.2.5 Material Fabrication and Pattern Process 653.2.5.1 Magnetron Sputtering 663.2.5.2 Ion Beam Deposition (IBD) 673.2.5.3 Evaporation 673.2.5.4 Chemical Vapor Deposition (CVD) 673.2.5.5 Photolithography 693.2.5.6 Etching 693.3 The Noise of TMR Sensors 703.3.1 The Source of Noise from TMR Sensors 703.3.2 Methods to Suppress the Noise 723.3.2.1 Increase the Number of MTJs in TMR Device 723.3.2.2 Optimize Free Layer Volume 733.3.2.3 Flux Concentrator 733.3.2.4 Applying a Bias Magnetic Field 743.4 TMR Sensors and Applications 753.4.1 TMR Read Heads 753.4.2 The TMR Angle Sensors 763.4.3 Geomagnetic Measurement 793.4.4 Spin-MEMS Combined Application 803.4.5 Nondestructive Testing (NDT) 823.4.6 Ultra-low Magnetic Field Detection: Biosensor 833.5 Conclusion 85References 864 Spin-Transfer Torque Materials and Devices for Magnetic Random-Access Memory (STT-MRAM) 93Yan Cui and Jun Luo4.1 The Background and Mechanism of STT-MRAM 934.1.1 The Background of STT-MRAM 934.1.2 The Mechanism of STT-MRAM 934.1.2.1 LLGS Equation 934.1.2.2 The Write Mechanism of STT-MRAM 944.1.2.3 The Magnetism of STT-MTJ 974.1.2.4 The Switching Properties of STT-MTJ 994.2 The Integrated Process of STT-MRAM 1024.2.1 CMP Technology 1024.2.2 Magnetic Film Deposition Technology 1034.2.3 Photolithography Technology 1034.2.4 Etching Technology 1034.2.5 Dielectric Isolation Technology 1044.2.6 Contact Technology 1044.2.7 Passivation Deposition 1044.3 Testing of the STT-MTJ Device 1054.4 The Development Status of STT-MRAM 105References 1075 Spin-Orbit Torque (SOT) Materials and Devices 113Yucai Li, Kevin William Edmonds, and Kaiyou Wang5.1 Spin-Orbit Coupling in Materials 1135.2 Manipulation of Magnetic Materials by SOT 1165.2.1 The Mechanism of SOT in Ferromagnets 1165.2.2 Measurement Techniques of SOT 1175.2.3 Field-Free SOT Magnetization Switching in Ferromagnets 1195.2.4 Domain Wall and Skyrmion Motion Driven by SOT 1215.2.5 Manipulation of Antiferromagnets by SOT 1225.3 SOT Materials 1235.3.1 Traditional Materials 1235.3.2 Interfacial Engineering 1245.3.3 Oxide Heterostructures 1255.3.4 The van der Waals Materials and Topological Materials 1255.4 Devices and Application 1285.4.1 SOT-MTJ and SOT-MRAM 1285.4.2 In-memory Computing 1295.4.3 SOT Artificial Intelligence Device 1305.4.4 Internet of Things 1315.5 Conclusion 131References 1326 Spin Oscillators 139Huayao Tu and Zhongming Zeng 6.1 Introduction 1396.2 Fundamental Physics 1406.2.1 Spin Transfer Torque and Magnetization Dynamics 1406.2.2 Spin Hall Effect (SHE) and Spin-Orbit Torque (SOT) 1416.2.3 Operation Principle of SO 1426.3 Device Classification 1436.3.1 Geometries 1436.3.2 Magnetic Equilibrium States 1456.3.3 Material Structures 1456.3.3.1 Spin Valves 1456.3.3.2 Magnetic Tunnel Junctions 1466.3.3.3 Bilayer 1466.3.3.4 Single Layer 1476.4 Emerging Spin-torque Oscillators Based on Magnetic Solitons 1486.4.1 Vortex 1486.4.2 Skyrmion 1496.5 Functional Properties 1506.5.1 Frequency 1506.5.1.1 Modulation Properties 1526.5.2 Output Power 1526.5.3 Linewidth 1556.5.4 Phase-locking and Synchronization 1576.6 Applications 1596.6.1 Microwave Source 1596.6.2 Spin Wave Emitter 1606.6.3 Microwave Detector and Energy Harvester 1606.6.4 Magnetic Field Detector 1636.6.5 Neuromorphic Computing 1646.7 Summary and Outlook 166References 1677 Magnetic Tunnel Junctions for Artificial Neural Network 179Meiyin Yang, Tengzhi Yang, and Jun Luo7.1 Introduction of Neural Computing 1797.2 Hardware Requirements for an Artificial Intelligence Neural Network 1827.3 Introduction to Magnetic Tunnel Junction Devices 1837.4 Magnetic Tunnel Junction for Neuron Hardware 1857.4.1 Introduction of STT-MTJ and SOT-MTJ 1857.4.2 Different MTJ-Based Neuron Hardware 1867.4.2.1 Step Function 1877.4.2.2 Nonlinear Activation Function 1887.4.2.3 Spike or Probability Based Neuron 1897.5 Magnetic Tunnel Junctions for Synaptic Devices 1927.6 Learning Methods Suitable for MTJs 1947.7 Summary and Outlook 195References 1958 Three-Dimensional Magnetic Structures of B20 Chiral Magnets 203Kejing Ran, Dongsheng Song, Weiwei Wang, Haifeng Du, and Shilei Zhang8.1 Theoretical Development 2038.2 Observation Technique 2068.2.1 Electron Holography 2068.2.1.1 Historical Survey 2068.2.1.2 Experimental Setup 2078.2.2 Resonant Elastic X-ray Scattering 2098.2.2.1 Historical Survey 2098.2.2.2 Theoretical Treatment 2108.2.2.3 Experimental Setup 2128.3 Experimental Results 2148.3.1 Magnetic Bobbers 2148.3.2 Surface Twists 216References 2179 Multiferroelectric Materials  221Xiaobin Guo and Li Xi9.1 Electric Field-driven Magnetization Switching 2229.2 Electric Field-driven Exchange Bias Reversal and Antiferromagnetic Domain Wall Motion 2299.3 Electric Field-driven Antiferromagnetic Vector Switching 237Acknowledgements 239References 24010 Robust Manipulation of Magnetic Properties in (Ga,Mn)As 243Hailong Wang and  Jianhua Zhao10.1 Background and Introduction 24310.2 Electric Field Effects on the Magnetic Properties of (Ga,Mn)As 24510.3 Manipulation of the Magnetism in (Ga,Mn)As by Light and Strain 25610.4 Giant Modulation of Magnetism via Organic Molecules 25710.5 Conclusion and Outlook 260Acknowledgements 262References 26211 Antiferromagnetic Materials and Their Manipulations  271Xionghua Liu and Kaiyou Wang11.1 Introduction 27111.2 Antiferromagnetic Materials 27211.2.1 Metallic Antiferromagnets 27211.2.2 Insulating Antiferromagnets 27311.2.3 Semiconducting and Semimetallic Antiferromagnets 27411.3 Manipulations of Antiferromagnetic States 27511.3.1 Magnetic Control of Antiferromagnets 27511.3.2 Strain Control of Antiferromagnets 27711.3.3 Optical Control of Antiferromagnets 27911.3.4 Electrical Control of Antiferromagnets 28111.4 Topological Antiferromagnetic Spintronics 28311.5 Summaries and Prospects 286References 28612 Prospects 295Meiyin Yang and Kaiyou WangIndex 299