The magnetization reversal and magnetic impedance (MI) of films and film elements based on Fe19Ni81 and Fe72.5Cu1.1Nb1.9Mo1.5Si14.2B8.7alloys with a varied thickness, heat-treatment temperature, and...

The temperature dependencies of magnetoimpedance (MI) and stress impedance (SI) were analyzed both in the as-quenched soft magnetic Co_68.5Fe₄Si₁₅B_12.5 ribbons and after their heat treatment at 425 K for 8 h. It was found that MI shows weak changes under the influence of mechanical stresses in the temperature range of 295–325 K and SI does not exceed 10%. At higher temperatures, the MI changes significantly under the influence of mechanical stresses, and SI variations reach 30%. Changes in the magnetoelastic properties for the different temperatures were taken into consideration for the discussion of the observed MI and SI responses. The solutions for the problem of thermal stability of the magnetic sensors working on the principles of MI or SI were discussed taking into account the joint contributions of the temperature and the applied mechanical stresses.

Soft magnetic materials are widely requested in electronic and biomedical applications. Co-based amorphous ribbons are materials which combine high value of the magnetoimpedance effect (MI), high sensitivity with respect to the applied magnetic field, good corrosion stability in aggressive environments, and reasonably low price. Functional properties of ribbon-based sensitive elements can be modified by deposition of additional magnetic and non-ferromagnetic layers with required conductivity. Such layers can play different roles. In the case of magnetic biosensors for magnetic label detection, they can provide the best conditions for self-assembling processes in biological experiments. In this work, magnetic properties and MI effect were studied for the cases of rapidly quenched Co₆₇Fe₃Cr₃Si₁₅B₁₂ amorphous ribbons and magnetic Fe₂₀Ni₈₀/Co₆₇Fe₃Cr₃Si₁₅B₁₂/Fe₂₀Ni₈₀ composites obtained by deposition of Fe₂₀Ni₈₀ 1 μm thick films onto both sides of the ribbons by magnetron sputtering technique. Their comparative analysis was used for finite element computer simulations of MI responses with different types of magnetic and conductive coatings. The obtained results can be useful for the design of MI sensor development, including MI biosensors for magnetic label detection.

A description of the method of magnetoimpedance tomography is presented. This method is based on the analysis of the frequency dependences of the impedance obtained in magnetic fields of various strengths. It allows one to determine the distribution of electrical and magnetic properties over the cross-section of the conductor, as well as their dependence on the magnetic field. The article proposes a specific approach to the implementation of the magnetoimpedance tomography method based on computer modeling by the finite element method. The results of this method are presented for composite Cu₉₈Be₂/Fe₂₀Co₆Ni₇₄ wires of the “highly conductive core–magnetically soft coating” type and amorphous rapidly quenched Co₆₆Fe₄Nb_2.5Si_12.5B₁₅ wires.