Multilayered Magnetic Wires and Films for Electromagnetic Sensor Technology L V. Panina* 1,2 , D.P. Makhnovskiy 2 , A. Zhukov 1 and J. Gonzalez 1 1 Departamento de Física de Materiales, Universidad del Pais Vasco, 20009 San Sebastian, Spain, 2 School of Computing, Communications and Electronics, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK, lpanina@plymouth.ac.uk Keywords: glass coated microwires, magnetic multilayers, magnetoimpedance, induced magnetic anisotropy, sensor circuit, tuneable composite materials Abstract. The discovery of the magnetoimpedance (MI) effect in 1994 had a strong impact on the development of magnetic sensors, offering miniature, highly sensitive, and quick response elements. Along with traditional areas of sensing applications (data storage, bio-medical electronics, robotics and security), the MI elements have a high potential for non-destructive testing (as eddy current probes) and smart sensory systems (self-sensing composites). In certain soft magnetic materials, such as composites of amorphous thin wires, the impedance change (MI ratio) can be as high as 600 % in the MHz band and 50-100% at GHz frequencies subjected to small magnetic fields or stresses. Furthermore, special thin-film structures have been proposed to improve the MI performance in miniature elements. This paper discusses physical concepts of MI in multilayered structures including MI ratio enhancement and effect of anisotropy, experimental results proving high sensitivity to the external stimuli for excitation frequencies up to few GHz, practical sensor designs and, finally, the use of MI fibers for tagging the composites to build-in sensing functionality . Introduction Miniature solid state magnetic-sensor technology has numerous applications for advanced intelligent measurement and control systems. Along with traditional areas of sensing applications (data storage, bio-medical electronics, robotics and security), solid state magnetic sensors are of high interest in non-destructive testing (NDT) and smart systems offering such functionalities as non-contact operation, high sensitivity, frequency multiplexing, quick response, and high spatial resolution. The demand in magnetic sensors has been satisfied in some areas by magneto-resistance, giant magneto-resistance, fluxgate and other technologies. A relatively new magnetic sensor technology based on the magnetoimpedance (MI) effect has the potential to overtake these sensor systems in terms of performance and low cost [1-3]. The present paper reviews the MI effect in multilayered magnetic wires and films in the context of its application for NDT and smart sensory materials. The MI sensing performance is based on enormous changes in the high frequency impedance of a soft magnetic material when its static magnetic structure undergoes transformation due to application of a magnetic field, stress or temperature [4-6]. The nominal ratio of the impedance change, called the MI ratio, reaches several hundred percents at MHz frequencies[7,8] and about 50-100% at GHz frequencies [9,10] in amorphous Advances in Science and Technology Vol. 54 (2008) pp 29-40 online at http://www.scientific.net © (2008) Trans Tech Publications, Switzerland Online available since 2008/Sep/02 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 158.227.160.32-12/09/08,20:52:30)