PUBLIKACJE KSIAZKI DYDAKTYKA REDAKCJA PE DOKTORANCI ENGLISH

CV PUBLICATIONS BOOKS JOURNAL PE

INSTITUTE OF PHYSICS

SERIES ON SENSORS

THIN FILM MAGNETORESISTIVE SENSORS

ISBN 0 7503 0702 1

IOP Publishing Ltd. 2001

Bristol and Philadelphia

CONTENTS         

 1             AMR SENSORS

1.1  Anisotropic magnetoresistive effect in thin ferromagnetic films                                  1

1.1.1. Essential information about the magnetoresistive effects                                       1

1.1.2. The origin of anisotropic magnetoresistance in ferromagnetic metals                8

1.1.3. The theory of magnetoresistance in ferromagnetic metals                                  12

1.1.4. Thin ferromagnetic film as the magnetic field sensor                                            17

1.1.5. Applying the Stoner-Wohlfarth model for analysis of
           magnetoresistive effects                                                                                                     22
 

1.2.     Biasing and stabilizing techniques                                                                                   27

1.2.1. The biasing and stabilizing fields in ferromagnetic
                 magnetoresistors                                                                                                            27

1.2.2. The real thin film the multidomain structure and the

          dispersion of anisotropy                                                                                                       33

1.2.3. The sensors biased by the hard magnetic layer                                                    45

1.2.4. The sensors biased by the current conducting layer                                             52

1.2.5. Biasing by exchange coupled antiferromagnetic layer                                          58

1.2.6. The soft adjacent layers (SAL) biasing technique                                                  63

1.2.7. Dual element sensors                                                                                                 70

1.2.8. AC biasing techniques                                                                                                76

1.2.9. The reverse mode of biasing                                                                                     81 

1.3.  Design and performances of AMR sensors                                                                    83

1.3.1. The influence of the sample geometry on the MR effect                                       83

1.3.2. The influence of magnetization non-uniformity on the MR effect                         89

1.3.3. Technological factors affecting the performances of AMR sensors                   97

1.3.4. The design and construction of AMR sensors                                                     115

1.3.5. The performances of AMR sensors                                                                       132

1.4. References                                                                                                                             159

 

2.            GMR SENSORS  

2.1.  Giant magnetoresistive effects                                                                                         165

2.1.1. An historical review and the main terms                                                                 165

2.1.2  Oscillatory exchange coupling in the magnetic multilayers                                173

2.1.3. Other coupling effects in multilayer structures                                                      185

2.1.4. Theoretical models of giant magnetoresistance                                                  191

2.1.5. Ferromagnetic multialayers as magnetic field sensors                                      199 

2.2.  Various types of GMR structures                                                                                      209

2.2.1. Structures with aniferromagnetic coupling                                                             209

2.2.2. Granular GMR structures                                                                                            217

2.2.3. Spin valve structures with asymmetric magnetic layers

          (uncoupled structures)                                                                                                 222

2.2.4. Spin valve structures with exchange biased layer                                                 229

2.2.5. Current perpendicular to plane (CPP) structures                                                  241

2.2.6. Magnetic tunnel junction (MTJ) structures                                                               247

2.2.7. Colossal magnetoresistance (CMR) thin film structures                                     251

2.2.8. Giant magnetoimpedance (GMI) structures                                                            256 

2.3.  Preparation, design and performances of GMR sensors                                            260

2.3.1. The deposition of thin film GMR structures                                                             260

2.3.2. Technological factors affecting the performances of

 GMR sensors                                                                                                               266

2.3.3. The shape effects in thin film GMR devices                                                            276

2.3.2. Design and construction of GMR sensors                                                              286

2.4.  References                                                                                                                              299

 

3. APPLICATIONS OF THE MAGNETORESISTIVE SENSORS 

3.1. Magnetic measurements                                                                                                     325

3.1.1. Magnetometers and compasses                                                                             325

3.1.2 Gradiometers, magnetic anomaly detection                                                           336 

3.2. Electrical measurements                                                                                                    341

3.3. Current transducers                                                                                                       341

3.4. Electrical transducers, switching and logic elements                                             347 

3.3. Magnetoresistive elements in data storage applications                                            353

3.3.1. Magnetic Random Access Memory (MRAM) devices                                            353

3.3.2. Magnetic card readers                                                                                                357

3.3.3. Magnetoresistive heads for tapes and discs applications                                  361

3.3.4. Unshielded magnetoresistive reading heads                                                       372

3.3.5. Shielded magnetoresistive heads                                                                           376

3.3.6. Yoke-type magnetoresistive heads                                                                          382 

3.4. Transducers of mechanical values                                                                                   384

3.4.1. Transducers of linear displacement                                                                        384

3.4.2. Transducers of angular position                                                                               391

3.4.3. Measurements of rotational speed                                                                          396 

3.5. Material testing and magnetic field imaging                                                                   400

3.5.1. Material testing by means of thin film magnetoresistors                                     400

3.5.2. Magnetic imaging systems                                                                                        406

3.6. References                                                                                                                               417 

List of Symbols                                                                                                                               431

List of Abbreviations                                                                                                                      433

Index                                                                                                                                                  435

TAYLOR&FRANCIS

SERIES ON SENSORS

PRINCIPLES OF ELECTRICAL MEASUREMENTS

ISBN 0 7503 1038 3

CRC Press 2006

New York, London

CONTENTS 

1. Introduction to Measurements                                                                       1

 

2. Fundamentals of Electrical Measurements                                                13

2.1. Main Terms and Definitions                                                                         13

      2.1.1. Basic terms of measurement technique                                           13

      2.1.2. The main methods of measurements                                               18

2.2. Uncertainty of Measurements                                                                     26

      2.2.1. Errors, uncertainty, and reliability of signal processing                  26

      2.2.2. Basic statistical terms and concepts                                                 34

      2.2.3. Methods of evaluation and correction of the uncertainty

                related to limited accuracy of measuring devices                            40

      2.2.4. The estimation of uncertainty in measurements                             52

2.3. Standards of Electrical Quantities                                                             57

      2.3.1. Standards, etalons, calibration and validation                                 57

      2.3.2. The standards of electrical quantities referred to
                the physical phenomena and laws                                                     58

      2.3.3. Material standards of electrical quantities                                        63

      2.3.4. The reference multimeters and calibrators                                      69

References                                                                                                               71

 

3. Classic Electrical Measurements                                                                 73

3.1. Indicating Measuring Instruments                                                             73

      3.1.1 Electromechanical instruments versus digital

               measuring systems                                                                                73

      3.1.2. The moving coil meters                                                                        74

      3.1.3. The moving iron meters                                                                        81

      3.1.4. Electrodynamic meters wattmeters                                                82

      3.1.5. Induction type watt-hour meters                                                          86

3.2. Recording and Displaying Measuring Instruments                                88

      3.2.1. Fundamentals of oscilloscopes                                                         88

      3.2.2. Recorders and data storage devices                                                93

3.3. Bridge Circuits                                                                                                94

      3.3.1. Balanced and unbalanced bridge circuits                                        94

       3.3.2. Null-type DC bridge circuits                                                                 96

      3.3.3. The AC bridge circuits                                                                           99

      3.3.4. The transformer bridge circuits                                                         104

      3.3.5. The unbalanced bridge circuits                                                         107

      3.3.6. The alternatives for bridge circuits Anderson Loop                   112

3.4. Potentiometers and Comparators                                                           114

References                                                                                                             118

 

4. Processing of the Analogue Measurement Signals                                121

4.1. Signal Conditioning                                                                                       121

      4.1.1. Analogue measurement signals                                                       121

      4.1.2. Conditioning of resistance, capacitance and inductance             126

      4.1.3. AC/DC conversion                                                                                 131

      4.1.4. Voltage to frequency conversion                                                         141

4.2. Amplification of the Signals                                                                        143

      4.2.1. Differential, operational and instrumentation amplifiers               143

      4.2.2. Isolation amplifiers                                                                               147

      4.2.3. Amplifiers of very small DC signals                                                  150

      4.2.4. Amplifiers of very small AC signals                                                   154

      4.2.5. Amplifiers of very large input resistance (electrometers)             159

      4.2.6. The function amplifiers                                                                        161

4.3. Negative Feedback in the Measuring Technique                                  169

4.4. The Improvement of the Quality of the Analogue Signals                   179

      4.4.1. The noises and interferences of the analogue signals                179

      4.4.2. The connection of the measuring signal to the amplifier             184

      4.4.3. The analogue filtering of the signals                                                191

References                                                                                                             201

 

5. Digital Processing of the Measurement Signals                                      205

5.1. Analogue-to-Digital Converters                                                                  205

      5.1.1. Sampling, quantization and coding of signals                                205

      5.1.2. Analogue-to-digital converters ADC                                                  218

      5.1.3. The main specifications of analogue-to-digital converters           234

5.2. Digital-to-Analogue Converters                                                                  238

      5.2.1. The reconstruction of the analogue signal                                       238

      5.2.2. The digital-to-analogue converters DAC                                           242

      5.2.3. The main specifications of digital-to-analogue converters           247

5.3. Methods and Tools of Digital Signal Processing                                    249

      5.3.1. The main terms of digital signal processing                                   249

      5.3.2. The Discrete Fourier Transform DFT and Fast Fourier

                Transform FFT                                                                                         259

      5.3.3. Short-time Fourier Transform and Wavelet transform                    268

      5.3.4. Digital filters                                                                                            275

 5.4. Examples of Application of Digital Signal Processing

       in Measurements                                                                                            287

      5.4.1. The spectral analysis                                                                            287

      5.4.2. Digital signal synthesis                                                                        297

      5.4.3. Improvement of the signal quality and the signal recovery            303

5.5. Digital Measuring Instruments                                                                    312

      5.5.1. Digital multimeters and frequency meters                                        312

      5.5.2. Digital oscilloscopes                                                                             318

      5.5.3. Digital measurement of power and energy                                      323

5.6. Intelligent Data Analysis                                                                                326

      5.6.1 The artificial intelligence in measurements                                      326

      5.6.2. The adaptive filters                                                                                 327

      5.6.3. Artificial neural networks                                                                       331

      5.6.4. Fuzzy Logic                                                                                               340

References                                                                                                                344

 

6. Computer Measuring Systems                                                                       349

6.1 Introduction                                                                                                       349

6.2. Input Circuits of the Measuring Systems                                                 353

      6.2.1. Circuits for data conditioning and acquisition                                  353

      6.2.2. The sensors with built-in interface intelligent sensors               354

      6.2.3. Analogue and digital transmitters                                                       356

      6.2.4. Data loggers                                                                                           357

      6.2.5. IEEE P1451 standard smart sensors                                            359

6.3. Data Acquisition Circuits DAQ                                                                 362

      6.3.1. Plug-in data acquisition board                                                            362

      6.3.2. External data acquisition board                                                           365

6.4. Data Communication in Computer Measuring Systems                       367

      6.4.1. Interfaces, buses and connectors                                                      367

      6.4.2. Serial interfaces: RS-232C and RS-485                                           368

      6.4.3. Serial interfaces: USB and FireWire                                                   373

      6.4.4. Parallel GPIB interface (IEEE-488/IEC-625)                                     377

      6.4.5. Wireless interfaces: IrDA, Bluetooth and WUSB                              382

      6.4.6. Mobile telephony systems GSM and UMTS as a tool
                for data transfer                                                                                        385

      6.4.7. Radio data acquisition and transfer                                                   389

      6.4.8. Computer systems using Ethernet and Internet                              392

      6.4.9. Dedicated interfaces: CAN, I2C, MicroLAN, SDI-12                         396

      6.4.10. HART interface and the 4 20 mA standard                                  400

      6.4.11. Industrial communication standards Fieldbus, Profibus,

                 SCADA                                                                                                      401

      6.4.12. Modular systems VXI, PXI                                                               406

      6.4.13. Standard command for measuring devices SCPI                     408

6.5. Measuring Systems Basing on the Signal Processors                        410

      6.5.1. Microcontrollers and signal processors
                in measuring technique                                                                         410

      6.5.2. Microinterfaces SPI and UART                                                         418

6.6. Virtual Measuring Systems                                                                          421

      6.6.1. What is the virtual measuring device?                                               421

      6.6.2. TestPoint                                                                                                  424

      6.6.3. Agilent VEE Pro                                                                                       428

      6.6.4. LabVIEW of National Instruments                                                       431

6.7. The Examples of Computer Measuring Systems                                   438

      6.7.1. The measuring system for testing of magnetic materials             438

      6.7.2. The arbitrary wave excitation systems                                               442

      6.7.3. The scanning device for magnetic field imaging                             449

References                                                                                                               452

 

Symbols used in the Book                                                                                     455

Abbreviations used in the Book                                                                            457

Index                                                                                                                           461