Expanding the longitudinal magnetoimpedance sensor range by direct bias current

We investigated the effects of induced helical anisotropy and application of dc bias current I-B on longitudinal magnetoimpedance (MI) in amorphous microwires both separately and together. We demonstrated that when both parameters are present, i.e., a dc bias current I-B is applied to the microwire with induced helical anisotropy, the longitudinal MI sensor range can be considerably extended up to the fields considerably higher than its anisotropy field as the slope of MI curve dZ/dH(E) remains rather high. A highly asymmetric longitudinal MI dependence with a rather high slope at the zero-field point was obtained. Reversing the bias current I-B causes reversal of the bias field direction and results in a mirroring of the MI dependence. This gives a possibility to determine both the sign and the magnitude of the external magnetic field. The obtained results can be used in development of the longitudinal MI sensors with increased sensitivity and/or range. (C) 2013 AIP Publishing LLC.