Magnetic Materials for Thin Film Based Magnetoimpedance Biosensing

Abstract

One of the fundamental characteristics of a magnetic field detector is sensitivity to the external magnetic field. Of all the known magnetic effects, the giant magnetoimpedance (MI) has the highest sensitivity with respect to the external magnetic field. Here, we describe our experience in designing, fabrication, experimental and theoretical characterization of [FeNi(50 nm)/Ti(6 nm)]6/Cu(500 nm)/[Ti(50 nm)/FeNi(6 nm)]6 multilayered structures for biometric detector. The designed device operates at room temperature, with a maximum sensitivity of the order of 0.4 Ohm/Oe for the total impedance and its real part and 0.1 Ohm/Oe for the imaginary part of the total impedance. An automatic system based on a ZVA-67 (Rohde & Schwarz) vector network analyzer was built for one-scan microwave absorption studies of both magnetoimpedance and ferromagnetic resonance of multilayered sensitive elements. Measurements were made with the coplanar line type holder in the increasing and decreasing fields. The obtained experimental and theoretical results for MI range were in a satisfactory agreement with each other. They could be useful for optimization of the MI multilayered elements for practical applications, including applications in different types of magnetic biosensors.