Magnetoimpedance effect in electrodeposited NiFe/Cu wire using trisodium citrate additive in plating bath

Abstract

Magnetoimpedance (MI) and magnetic properties of the electroplated NiFe/Cu thin films with a steadily rising concentration of trisodium citrate (TSC) additive in the plating bath is systematically examined in a wide frequency range of 10 kHz–8 MHz. The addition of TSC to the plating bath reduces the crystalline size and coercivity of the NiFe film, resulting in increased magnetic softness and MI ratio. The grain refining action of TSC additive is responsible for the random distribution of magnetic anisotropy axis in individual tiny crystallite which enhance circumferential permeability of deposited film and its MI ratio. The optimum concentration of TSC additive is found to be 40 g/l and sample electrodeposited at that TSC concentration boosts the MI ratio to 113% as compared to 28% when no TSC is used. When the film is deposited without any additive, a typical double peak behavior of the MI response curve is exhibited at higher frequency. This feature is eradicated with slightest inclusion of TSC additive in the electrodeposition bath which is an indication that inclusion of trisodium citrate weakens the circumferential anisotropy in plated film. Based on the analytical formulation of circumferential permeability the results of MI measurements are mapped with the theoretical framework, and the circumferential permeability of the NiFe magnetic film is reconstructed by curve fitting. Through the investigation of the fitting parameters, it is found that the addition of TSC to the bath completely annihilates the circumferential anisotropy found in as deposited permalloy film which is responsible for the transition from double to single peak behavior of MI response at higher frequencies.