Thin Film Magnetoresistive Sensors presents a comprehensive review of thin film magnetoresistive (MR) sensors, including the theory of MR effects as well as the design, fabrication, properties, and applications of MR sensors. With over 1,000 references, the book fully reviews the theory, development, and use of these sensors. It provides essential information about the performance of various kinds of sensors, including permalloy magnetoresistors, spin valve sensors, multilayer sensors, colossal effect sensors, spin dependent tunneling sensors, and magnetoimpedance sensors.
Divided into three independent parts, the book first concentrates on the most widely used sensors-anisotropic magnetoresistive sensors (AMR). The second part deals with giant magnetoresistive (GMR) sensors, including those still in development. In the third section, the book describes the applications of MR sensors, especially in data storage systems, industrial measurements, and nondestructive material testing systems.
Preface. 1 AMR Sensors. Anisotropic magnetoresistive effect in thin ferromagnetic films. Essential information about magnetoresistive effects. The origin of anisoptropic magnetoresistance in ferromagnetic metals. Thin ferromagnetic film as the magnetic field sensor. Applying the Stoner-Wohlfarth model for analysis of magnetorestive effects. Biasing and stabilizing techniques. The biasing and stabilizing fields in ferromagnetic magnetoresistors. The real thin film - the multidomain structure and the dispersion of anisotropy. The sensor biased by the hard magnetic layer. The sensors biased by the current conducting layer. Biasing by exchange coupled antiferromagnetic layer. The soft adjacent layers (SAL) biasing technique. Dual element sensors. AC biasing techniques. The reverse mode of biasing. Design and performances of AMR sensors. The influence of the sample geometry on the MR effect. The influence of magnetization non-uniformity on the MR effect. Technological factors affecting the performances of AMR sensors. The design and construction of AMR sensors. The performances of AMR sensors. References. 2 GMR Sensors. Giant magnetoresistive effects. An historical review and the main terms. Oscillatory exchange coupling in the magnetic multilayers. Other coupling effects in multilayer structures. Other coupling effects in multilayer structures. Theoretical models of giant magnetoresistance. Ferromagnetic multilayers as magnetic field sensors. Various types of GMR structures. Structures with antiferromagnetic coupling. Granular GMR structures. Spin-valve structures with asymmetric magnetic layers (uncoupled structures). Spin Valve structures with exchange-biased layer. Current perpendicular to plane (CPP) structures. Magnetic tunnel junction (MTJ) structures. Giant magnetoimpedance (GMI) structures. Preparation, design and properties of GMR sensors. The deposition of thin film GMR structures. Technological factors affecting the performances of GMR sensors. The shape effects in thin film GMR devices. Design and construction of GMR sensors. References. 3 Applications of Magnetorisistive Sensors. Magnetic measurements. Magnetometers and compasses. Gradiometers, magnetic anomaly detection. Electrical measurements. Current transducers. Electrical transducers, switching and logic elements. Magnetoresistive elements in data storage applications. Magnetic Random Access Memory (MRAM) devices. Magnetic card readers. Magnetoresistive heads for tape and disk applications. Unshielded magnetoresistive reading heads. Shielded magnetoresistive heads. Yoke-type magnetoresistive heads. Transducers of mechanical values. Transducers of linear displacement. Transducers of angular position. Measurements of rotational speed. Materials testing and magnetic field imaging. Material testing by means of thin film magnetoresistors. Magnetic imaging systems. References. List of Symbols. List of Abbreviations. Index