Magnetostatic interaction in multi-shell Ni80Fe20/Cu composite wires

Highlights: • GMI effect is a sensitive tool to study the magnetic properties of composite wires. • The magnetostatic interaction depends on the domain structure of the near neighbor coating layer. • The dipole–dipole interaction will conversely affect magnetic properties of multilayer composite wires. Magnetostatic interaction in multilayered structure materials has long been a key to optimize the magnetic devices due to the modulation of their magnetic properties. In this study, the multi-shell Ni₈₀Fe₂₀(t_out)/Ni₈₀Fe₂₀(t_in)/Cu composite wires were prepared by magnetron sputtering. The results show that the hysteresis loops of the multi-shell composite wires do not present significant changes compared with the single shell composite wire. A four-peak structure GMI profile may appear when both the inner and outer Ni₈₀Fe₂₀ shell have a preferred circular anisotropy, which indicated that the strong dipole interactions existed between the shells. In such multi-shell system, the response of dipole field H_di to the driving frequency is against the compensation field H_comp. If the inner shell has axial anisotropy structure, there are almost no dipole interaction observed according to disappearance of the interaction energy. All the results suggest a facile way to achieve a higher GMI response, and a sensitive method, especially in the low magnetic field region, to investigate the magnetic interactions in complicated composite structure materials.