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Giant Magnetoresistance (GMR) Sensors from Basis to State-Of-The-Art Applications Smart Sensors, Measurement and Instrumentation

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Giant Magnetoresistance (GMR) Sensors from Basis to State-Of-The-Art Applications Smart Sensors, Measurement and Instrumentation Smart Sensors, Measurement and Instrumentation 6 Càndid Reig Susana Cardoso de Freitas Subhas Chandra Mukhopadhyay Giant Magnetoresistance (GMR) Sensors From Basis to State-of-the-Art Applications Smart Sensors, Measurement and Instrumentation Volume 6 Series Editor Subhas Chandra Mukhopadhyay School of Engineering and Advanced Technology (SEAT) Massey University (Manawatu) Palmerston North New Zealand E-mail: [email protected] For further volumes: http://www.springer.com/series/10617 Càndid Reig · Susana Cardoso de Freitas, Subhas Chandra Mukhopadhyay Giant Magnetoresistance (GMR) Sensors From Basis to State-of-the-Art Applications ABC Càndid Reig Dr. Subhas Chandra Mukhopadhyay Department of Electronic Engineering School of Engineering and University of Valencia Advanced Technology Burjassot Massey University (Manawatu) Spain Palmerston North New Zealand Susana Cardoso de Freitas INESC-MN Rua Alves Redol Lisboa Portugal ISSN 2194-8402 ISSN 2194-8410 (electronic) ISBN 978-3-642-37171-4 ISBN 978-3-642-37172-1 (eBook) DOI 10.1007/978-3-642-37172-1 Springer Heidelberg New York Dordrecht London Library of Congress Control Number: 2013933304 c Springer-Verlag Berlin Heidelberg 2013 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broad- casting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher’s location, in its cur- rent version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the Copyright Clearance Center. Violations are liable to prosecution under the respective Copyright Law. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Giant Magnetoresistance (GMR) Sensors Editorial The spintronics concept was stated during the eighties in order to describe charge trans- port mechanisms in which the spin of the electrons play an important rule. The Giant Magnetoresistance effect, reported at the end of this decade, was the definitive step in pushing this concept towards technological applications. Initially, read heads in hard disk drives were benefited of this emerging technology. The bits magnetically saved onto the surface of the disk are read by the binary changing of the resistance of GMR devices. With the time, and taking advantage of the gained knowledge from this re- search, new multilayered structures were engineered in order to make use of the linear capabilities of these devices. Their inherent properties regarding high sensitivity, large scale of integration and compatibility with standard CMOS circuitry have proved def- inite advantages and have placed GMR devices as the preferable magnetic sensors in most of the current applications. This manuscript is dedicated to draw the scope of the state of the art of current mag- netic sensing applications based on GMR sensors. From the definition of the concepts to the analysis of several selected cases of success, the different topics related to this novel technology are described. In the first chapter, the theoretical fundamentals are introduced. The concepts of GMR, spin valve and tunneling magnetoresistance are presented. The descriptions of the physical mechanisms are analyzed, including the sensors based linear regime. The second chapter is dedicated to the involved microfabrication processes. Being multilayered micro-structures, the design and realization of GMR devices share some techniques with standard CMOS processes. Lithography, pattern transfer by lift-off or etching, . steps are commonly applied. Other processes such as magnetic layers deposition are specific to GMR technology and their compatibility with standard CMOS processes is a matter of concern. The range of detectivity of the GMR sensors is basically limited by the signal to noise ratio (SNR) instead of the signal level. A detailed description of the noise mech- anisms in GMR sensors is presented in the third chapter. The analysis is particularized to spin valves and magnetic tunnel junctions. The experimental setup for performing VI Giant Magnetoresistance (GMR) Sensors noise measurements is provided. Biasing strategies for minimizing noise effects are also proposed. A GMR sensor can be basically understood as a magnetic resistive sensor. In this sense, the traditional approaches developed for typical resistive sensors can be directly considered. For example, Wheatstone bridges are commonly used in GMR based sen- sors applications. Novel approaches such as current based biasing or resistive array read-out interfaces need to be specifically described. Chapter four analyses the state of the art of resistive sensors interfaces, focusing on GMR particularities and ranging from realization with discrete components to microelectronic designs. Microelectronics in general and the measurement of electric current at the integrated circuit (IC) level is one of the fields in which GMR sensors are applied. After the pre- sentation of the concept (to measure the electric current by means of the associated magnetic field) some cases of success are revised. Particular issues such as bandwidth limitations or self-heating effect are analyzed. Some applications are proposed. The compatibility with non-dedicated CMOS processes is also studied. The automotive world has also incorporated GMR sensors to its portfolio. In this chapter some developments regarding the use of GMR sensors in automobiles at In- fineon are presented. Such sensors can be used in steering angle measurement, rotor position measurement, wheel speed measurement and crank shaft speed. Data acquisi- tion and processing in these systems is also analyzed. Being magnetic sensors and due to their inherent advantages related to miniaturiza- tion, GMR sensors are also applied in compass magnetometers as those included in portable navigation devices such as global positioning systems (GPS) and other mobile gadgets, mainly smartphones. The compass indicates the static orientation of the user which, with the addition of gyroscopic information along with GPS data can give pre- cise location and orientation to the users. In this chapter, the fundamental concepts and the current trends of GMR based compass magnetometers are described. To give an idea of its maturity, GMR sensors have already left the earth and have been included as part of the instrumentation in experimental satellites. In this chapter, the use of commercial off-the-shelf GMR based 3D magnetic sensors on board a picosatellite is described. After a comparison of currently available alternative, the design of the considered system is presented. The system passed all the qualification processes. Highly promising results are being obtained when using GMR sensors in non- destructive evaluation (NDE) processes. Two complimentary chapters are dedicated to this topic. In the first one, the inspection of failures in printed circuit boards (PCBs) is approached. The explanation of the underlying physics (eddy-current testing, ECT), the description of the GMR based scanning probe as well as the associated electronic interface and the analysis of the results, also including finite element modeling (FEM) are treated. In the other chapter, an example of GMR sensors used in biomedicine is described. A needle probe, including GMR sensors is presented. An experimental setup and procedure with agar injected with magnetic fluid to simulate actual clinical process was developed. For improving the performance of NDE processes based on GMR sensors, the use of arrays can be considered. In the last chapter, this approach is analyzed; comparing figures of merit with previously stated systems such as SQUIDs, Hall effect or giant Giant Magnetoresistance (GMR) Sensors VII magnetoimpedance (GMI) based ones. Then the use of magnetoresistive sensors in imaging and scanning microscopy is particularly demonstrated for die level fault isolation. From all described work we can conclude that we can definitively change our ap- preciation on GMR sensors. In few years they have moved from being ‘potential’ to become the first option in much of the applications requiring the sensing of low magnetic fields. C`andid Reig Susana Cardoso de Freitas Subhas Chandra Mukhopadhyay VIII Giant Magnetoresistance
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