Giant magnetoimpedance: A label-free option for surface effect monitoring

The change in magnetoimpedance (MI) during surface modification of the magnetic sensitive element caused by highly corrosive fluid was studied with the aim of creating a robust method to monitor the surface effects. A MI-based sensor prototype with an as-quenched FeCoSiB or FeCoCrSiB amorphous ribbon sensitive element was designed and calibrated for a frequency range of 0.5-10 MHz at an intensity of the current of 10-60 mA without bath for fluids. Measurements as a function of the exposure time were also made in a regime where chemical surface modification and sensing were not separated (in a bath for fluids). The MI variation was explained by the change of the surface magnetic anisotropy and the geometry of the sensitive element. A simple model was developed to describe MI change. It was shown that the magnetoimpedance effect can be employed as useful method to probe the electric features of surface-modified magnetic electrodes when the corrosive fluid, the material of the sensitive element, and the detection conditions are properly selected. (c) 2007 American Institute of Physics.