Nanowires made of FeNi and FeCo alloys: synthesis, structure, and Mössbauer measurements

Nanowires have been formed from FeNi and FeCo alloys by the template synthesis method based on galvanic filling of pores of track membranes. A change in the nanowire elemental composition with a change in the electrolyte composition and with a change in the deposition potential has been studied. FeNi nanowires exhibit the effect of anomalous Fe codeposition: the iron content in the nanowires is much higher than that in the electrolyte. The difference increases with an increase in the initial concentration and with a decrease in the growth potential. It has also been found that the iron concentration increases in nanowire vertices. For FeCo nanowires, their composition corresponds to the electrolyte composition and changes only slightly with a change in the potential. An analysis of the X-ray diffraction data has determined the character of change in the spectra under varying growth conditions. The X-ray spectra of FeNi are found to depend on the growth potential (the intensity of phase peaks changes). Mössbauer measurements have revealed spontaneous magnetization for all samples of arrays of nanowires along their axes. The dependence of hyperfine magnetic field strength $B_{hf}$ at $^{57}$Fe nuclei on the composition of nanowires of Fe$_{x}$Co$_{1-x}$ and Fe$_{x}$Ni$_{1-x}$ solid solutions is obtained for the first time. It is found that the $B_{hf}$ value decreases with an increase in the electrodeposition rate (or with an increase in deposition potential $U$).