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Atomic structures of fabricated Fe-Co alloys were investigated real time by time resolved x-ray absorption spectroscopy (TRXAS) at annealing temperature of 400° C. The various compositions of Fe-Co alloy thin films were prepared by electro-deposition on indium-tin oxide glass substrate with iron sulfate and cobalt chloride electrolyte solutions. The current density of 80 A/m2 was used to deposit Fe-Co thin film with varying the ratio of Fe and Co ion concentrations. The Fe-Co alloys with boron nitride powders were mixed, grinded and pressed in the pallet form in order to insert into environmental controlled sample holder for TRXAS measurement. The samples were annealed under 20% oxygen and 80% nitrogen atmospheric by increasing the temperature up to 400° C and then remaining for an hour. The influence of annealing temperature can modify the atomic structures of Fe-Co alloys as indicated in the variation of extended x-ray absorption fine structure (EXAFS) peaks. Most of the EXAFS peaks followed the temperature profile i.e. increasing or decreasing during the temperature rising and then maintaining about constant values during holding the temperature at 400° C. By transforming the EXAFS peaks into scattering radius space, the modification of relative scattering amplitude from each nearest neighbor position indicated the atomic relocation during annealing the samples. Some of scattering patterns from Fe and Co oxides can be found and their amounts changed during rising the annealing temperature. In addition, the atomic relocations extracted from the Co absorption edge was very much smaller than those of Fe edge probably due to relative more stable of Co atomic positions for this range of annealing temperature.

The magnetic nanoparticles of cobalt-and nickel-iron oxide have been extensive interest due to their superparamagnetic properties and their potential applications in many fields. The iron, cobalt and nickel can stay in many oxidation states and are easily oxidized especially in ambient air therefore the composition and oxidation states of these oxides can be unintentionally modified. Usually, the composition and oxidation states in these magnetic nanoparticles are determined by various experimental techniques required a sample in solid phase. This may lead the nanoparticles to directly contact with air and change the state. In this study, the magnetic nanoparticles in colloidal phase with concentration of 24mg/ml, derived from co-precipitation process, were directly injected to liquid cell for X-ray absorption near-edge structure (XANES) measurement. The iron-, cobalt-or nickel-iron oxide nanoparticles were prepared by dissolving CoCl2/FeCl3 or NiCl2/FeCl3, respectively, in deionized water with various atomic ratios. The average iron oxide nanoparticle size obtained by dynamic light scattering is about 4.2 nm with polydispersity of 0.987. Spherical shape with some stabilizer layer was observed by transmission electron microscope. The iron content in various composition nanoparticles was estimated in liquid phase by the ratio between the Fe edge peak and Co or Ni edge peak. The oxidation states of metal ions were also derived from the linear fitting of standard compounds at particular oxidation states. The shifts of peak positions were examined to indicate the variation of oxidation state as well.