Magneto-impedance and Magnetic Relaxation in Electrodeposited Cu/Ni80Fe20 Core/Shell Composite Wire

The model for the magneto-impedance of composite wires composed of highly conductive nonmagnetic metal core and soft magnetic shell was derived based on the Maxwell's equations. The Cu(100 mu m diameter)/Ni80Fe20(15 mu m thickness) core/shell composite wire was fabricated by electrodeposition. The impedance spectra for the Cu/Ni80Fe20 core/shell composite wire were measured in the frequency range of 10 kHz similar to 10 MHz under longitudinal dc magnetic field in 0 Oe similar to 200 Oe. The spectra of complex permeability in circumferential direction were extracted from the impedance spectra by using the derived model. The extracted spectra of complex permeability showed relaxation-type dispersion which is well curve-fitted with Debye equation with single relaxation frequency. By analyzing the magnetic field dependence of the complex permeability spectra, it has been verified that the composite wire has magnetic anisotropy in longitudinal direction and the origin of the single relaxation process is the magnetization rotation in circumferential direction.