Magnetoimpedance Effect in Cobalt-Based Amorphous Ribbons with an Inhomogeneous Magnetic Structure

Abstract

The results of a computer simulation and experimental study of the magnetoimpedance effect (MI) in amorphous Co68.5Fe4.0Si15.0B12.5 and Co68.6Fe3.9Mo3.0Si12.0B12.5 ribbons in the ac frequency range from 0.01 to 100 MHz are presented. It was found that the maximum MI value exceeds 200%, which may be of interest in the development of magnetic field sensors. It is also shown that practically significant characteristics of the MI response strongly depend on the ac frequency, which is due to the inhomogeneous distribution of magnetic properties over the ribbon cross section. This distribution was studied using magnetoimpedance tomography based on the analysis of the experimental dependences of the reduced impedance on the ac frequency.

Theoretical Study of Microwires with an Inhomogeneous Magnetic Structure Using Magnetoimpedance Tomography

“…When we take into account the frequency dependence of the permeability and neglect the imaginary part of the permeability, then (Δ Z / Z ) max increases with the frequency (see curve 3 in Figure 5 ). Thus, the analysis demonstrates that the simplified approach developed previously [ 57 , 58 , 59 , 60 , 61 , 62 ] is valid within a wide frequency range. However, at high frequencies, the frequency dependence and the complex nature of the circumferential permeability should be taken into account in order to describe the MI response of amorphous microwires correctly.…”

“…It should be noted that there are no methods for the direct study of the magnetic structure in the cross-section of glass-coated amorphous microwires, so it is usually interpreted on the basis of magnetostatic measurements. Recently, a new method to evaluate magnetic structure in amorphous materials of different types exhibiting a MI effect was developed [ 56 , 57 , 58 , 59 , 60 , 61 , 62 ]. The method is based on measured data on the frequency dependence of the MI, which allows one to analyze the distribution of the permeability over the conductor cross-section.…”

“…The Maxwell equations were solved numerically by the finite element method by using Comsol Multiphysics commercial software ( ). The method allowed description of the experimental data on the MI frequency dependences in the composite CuBe/FeCoNi wires [ 57 , 58 , 59 ], amorphous rapidly quenched wires [ 57 , 60 , 62 ] and amorphous ribbons [ 61 ].…”

Enhanced Magnetoimpedance Effect in Co-Based Micron Composite CoFeNiSiB Ribbon Strips Coated by Carbon and FeCoGa Nanofilms for Sensing Applications

“…Meander MI elements have become a focus of structural optimization research. Many theoretical and experimental studies on enhanced MI effects in ribbon meanders have been reported [6][7][8][9]. Laser cutting and wet etching are the main fabrication methods for micro-patterned ribbons [10,11].…”