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Improved Magnetic Tunnel Junctions Design for the Detection of Superficial Defects by Eddy Currents Testing

Cardoso, FC ; Rosado, L. S. ; Franco, FR ; Ferreira, Ricardo Ferreira ; Paz, EP ; Cardoso, SC ; Ramos, P.M. ; Piedade, M. S. ; Freitas, PF

IEEE Transactions on Magnetics Vol. 50, Nº 11, pp. 1 - 4, November, 2014.

ISSN (print): 0018-9464
ISSN (online): 0018-9464

Journal Impact Factor: 1,129 (in 2008)

Digital Object Identifier: 10.1109/TMAG.2014.2326959

Abstract
In the last decade, magnetoresistive sensors attracted great interest for integration in eddy current-based non-destructive testing
due to their high sensitivity and signal to noise ratio in a large range of frequencies (from dc to hundreds of megahertz). In this
paper, a sensor composed of several magnetic tunnel junction (MTJ) elements in series is optimized and included in a custom
probe configuration for the detection of superficial defects. Since the signal magnetic fields are very low, a finite element modeling
simulation was supporting the sensor design optimization. The MTJ chips were microfabricated, assembled with the excitation coils
and used in experimental measurements of defects 400 ìm wide and 500 ìm deep. The experimental results obtained showed very
good agreement with the simulations.