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Off-diagonal magnetoimpedance in NiFe-Au-NiFe layered film and its application to linear magnetic sensors

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6 Author(s)
N. Fry ; Sch. of Comput., Univ. of Plymouth, UK ; D. P. Makhnovskiy ; L. V. Panina ; S. I. Sandacci
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We have measured the field dependence of the off-diagonal impedance in the megahertz frequency range for a NiFe-Au-NiFe layered film using a helical microcoil. The film and the coil were deposited by means of radio-frequency sputtering, and a transverse anisotropy in magnetic layers was established by applying a dc magnetic field during the deposition and by postproduction annealing. The film had 5 mm length, 50 μm width, and 1.5 μm total thickness. The helical microcoil had 23 turns with a 50 μm turn width. We applied high-frequency excitation by means of the coil current and measured the induced voltage across the film stripe. This voltage response is directly proportional to the off-diagonal component of the total impedance tensor. We found that the plots of the real and imaginary parts of the off-diagonal impedance, as functions of the applied dc magnetic field, are antisymmetrical with respect to the field direction. The dc bias current through the film plays an important role: without the bias current, the measured signal is very small and irregular. The field antisymmetry demonstrated by the off-diagonal impedance can be utilized in highly sensitive and linear magnetic sensors, and we discuss the principles of operation of such sensors here.

Published in:

IEEE Transactions on Magnetics  (Volume:40 ,  Issue: 5 )