For the purpose of developing a composite micro sensor for weak magnetic field, fabrication of high permeability ferromagnetic material is needed. The magnetic properties of the pulse-plated samples depend greatly on the chemical composition and nanocrystalline grain size of the ferromagnetic layer. In this study, the effect of the pulse plating parameter: duty cycle on the chemical composition and grain size of the deposited layer was investigated. A layer of soft ferromagnetic material Ni-Fe was deposited onto copper wires of 20µm diameter by means of pulse and dc plating and tested under XRD for grain size measurement. It was found that variations in duty cycle do not affect the thickness of the plated layer, but affect significantly the chemical composition. There is an optimum duty cycle for getting the minimum grain size of plated layer in pulse plating with saccharin. The results from the magnetic measurement showed that the permeability of the plated material increased greatly as the grain size decreased in the range of 10 – 55 nm.