Fractal pore distribution and magnetic microstructure of pulse-electrodeposited nanocrystalline Ni and Co - art. no. 054408

The crystalline and magnetic microstructures of nanocrystalline Ni and Co s amples, with volume-averaged grain sizes between 10 and 60 nm, obtained by pulsed electrodeposition have been studied by means of small angle neutron scattering (SANS), small angle x-ray scattering (SAXS), and magnetization m easurements. According to density measurements the porosity of the samples amounts to values between 0.5 and 3%. SAXS and nuclear SANS contributions a re dominated by pore scattering and reveal that the pores are distributed a ccording to a fractal correlation function. The magnetic SANS contributions measured at zero field indicate that both n-Ni and n-Co have magnetic doma ins with sizes exceeding 150 nm, i.e., the domains must confine several cry stallite grains. The present results of the domain sizes in n-Ni are simila r to earlier literature data. For the case of n-Co the present results diff er considerably from literature data, where only single-grain domains were found in n-Co samples synthesized by other methods. We attribute the differ ence in domain sizes in n-Co to the preparation method which in the present case yields samples of relatively high density. The field dependence of th e SANS signal observed in n-Ni and n-Co shows that large domains are satura ted at smaller fields than the smaller domains. The field dependence of the SANS signal is compared with the field dependence of the magnetization.