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This paper describes research on a magnetoresistive sensor consisting of two differentially connected Permalloy stripes with an overlay bias conductor [D.J. Mapps et al., A double bifilar magnetoresistor for earth's field detection, IEEE Trans. Magn. 23 (5) (1987) 2413-2415.]. A magnetic field derived from current flowing in the bias conductor switches the magnetisation in the sensor stripes alternately in opposite directions for each half-cycle of the bias field current. The material of the sensor is optimised for lowest Barkhausen noise [M.A. Akhter, D.J. Mapps, Y.Q. Ma, A. Petford-Long, R. Doole, Thickness and grain size dependence of the coercivity of permalloy thin film, J. Appl. Phys. 81 (8) (1997) 4122-4124.] and lowest demagnetising field. A number of sensors have been prepared with film thicknesses of 5-40 nm, stripe widths varying between 10 and 80 μm and a standard length of 6 mm. Barkhausen noise and corresponding hysteresis is studied by analysis of MR response of the group of sensors, together with their magnetoresistive hysteresis, which may be reduced or improved by using a suitable external high-frequency field (5-20 kHz). Variation in the sensitivity of the sensor to the magnitude of a switched-biasing field was measured by applying a very small alternating field (variable from a few tens to hundreds of nano-Tesla) and a varying transverse DC field component (δHx). Advantages and limitations of the sensors will be discussed in the paper. © 2000 Elsevier Science S.A. All rights reserved.
Author(s): Mapps DJ, Ma YQ, Akhter MA
Publication type: Article
Publication status: Published
Journal: Sensors and Actuators, A: Physical
Year: 2000
Volume: 81
Issue: 1-3
Pages: 60-63
ISSN (print): 0924-4247
ISSN (electronic): 1873-3069
Publisher: Elsevier
URL: http://dx.doi.org/10.1016/S0924-4247(99)00117-X
DOI: 10.1016/S0924-4247(99)00117-X
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