Structural and magnetic properties of Fex–C1−x nanocomposite thin films

Abstract

Iron–carbon nanocomposite thin films with iron concentrations ranging from 12 to 74 at. % were grown by ion-beam sputtering codeposition at different substrate temperatures. The microstructure of the films was characterized by transmission electron microscopy, atomic force microscopy, extended x-ray absorption fine structure, and grazing incidence small-angle x-ray scattering. A granular morphology consisting of body-centered-cubic iron-rich nanoparticles (2–5 nm in diameter and 3–8 nm in height with a relatively sharp size distribution) regularly distributed within a more or less graphitic matrix was obtained. Structural properties as well as magnetic ones were found to depend strongly on composition, substrate temperature, and postdeposition treatments (annealing or Ar+ irradiation). The temperature dependence of the susceptibility exhibited a superparamagnetic response with blocking temperature in the range of 13–180 K. The maximum low-temperature (5 K) coercivity value obtained in this study was 850 Oe for the film with the lowest iron content (x=0.12). The saturation magnetization was found to be reduced compared to the corresponding bulk value for pure α-Fe, and increased with increasing substrate temperature. Otherwise, when increasing the iron content, a decrease in coercivity was observed in correlation with an increase in remanent magnetization.

Evolution of catalyst particle size during carbon single walled nanotube growth and its effect on the tube characteristics

“…The estimated value of K is of the same order as reported before for Fe-C nanoparticles ͑K ϳ 1.7 ϫ 10 7 ergs/ cm 3 ͒. 40 One distinction in the ZFC curve in Fig. 6 is a flat maximum located around 150± 30 K, indicating a broad particle size distribution after carbon SWNT growth.…”

Magnetic nanodot arrays produced by direct laser interference lithography

“…Bubonneau et al have shown that in the related Fe-C system, the as-deposited films are composed of Fe nanoparticles embedded in a moreor-less graphitized C matrix. 12 It is known that the graphite phase ͑density of 2.2 g/cm 3 ) can transform into amorphous one ͑density of 1.6 g/cm 3 ) under thermal/laser treatment. 13,14 It is natural that this transformation is accompanied by the film thickness change.…”

Study of Relation Between Particle Size And Magnetic Saturation of Synthesized Undoped Iron Oxide

“…Saturation magnetization was very low 1 emu/gm. Results drawn for ferrites [1,2,6,7,10] and nanoparticles prepared by various method [8,9,11] were also found true for nano-Fe2O3 particles prepared by co-precipitation method. …”

“…Iron-rich nanoparticles of 2-8 nm were obtained. The saturation magnetization was found to decrease compared to the bulk value for pure α-Fe [9].Co-precipitation method was used to prepare Manganese ferrite, (MnFe2O4) fine particles in the size range 5-15 nm. The saturation magnetization again followed decreasing trend with decreasing size [10].…”