Multilayered Magnetic Wires and Films for Electromagnetic Sensor Technology
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 .
Pietro VINCENZINI and Giuseppe D'ARRIGO
L. V. Panina et al., "Multilayered Magnetic Wires and Films for Electromagnetic Sensor Technology", Advances in Science and Technology, Vol. 54, pp. 29-40, 2008