This thesis is about the magneto impedance tensor of Cu core/NiFe shell composite wire fabricated by electrodepositing soft magnetic NiFe shell on highly conductive Cu core wire. The first goal of this research is develop a theoretical model to analyze the frequency and magnetic field dependance of the impedance tensor components of Cu core/NiFe shell composite wire. The second goal is to fabricate Cu core/NiFe shell by electrodeposition and to characterize the measured frequency and magnetic field dependance of the impedance tensor components.
Theoretically, the equations expressing 4 components of impedance tensor for Cu core/NiFe shell are derived from Maxwell equations. These equations show that 4 components of impedance tensor have a correspondence on 4 components of permeability tensor. A model is presented to analyze frequency and magnetic field dependance of permeability tensor components.
Experimentally, Cu core/NiFe shell composite wire is fabricated by electrodeposition and the frequency spectra of impedance tensor components of the composite wire are measured at various external static magnetic fields.
The measured frequency spectra of diagonal components of the impedance tensor showed sensitive changes with external magnetic field while the spectra of off-diagonal components of the impedance tensor did not show any changes. The spectra of diagonal components of complex permeability tensor were extracted from the measured spectra of diagonal components of the impedance tensor. The extracted spectra of diagonal components of the complex permeability tensor showed relaxation type dispersion depending sensitively on magnetic field. It is found that the magnetic easy axis of the core/shell composite wire is near the length direction by analyzing the results with the developed models developed from this research.
The theoretical models and experimental results in this research will contribute to develope a magnetic sensor using the core/shell composite wite.