XPS and Magnetic Properties of CoFe₂O₄ Nanoparticles Synthesized by a Polyacrylamide Gel Route

Abstract

Cobalt ferrite CoFe 2 O 4 nanoparticles were prepared via a polyacrylamide gel route and were characterized by XRD, SEM, XPS and VSM. It is demonstrated that the sample (designated S1) prepared without using the cross-linking agent bis-acrylamide has an average grain size of 45 nm, while the sample (designated S2) prepared by introducing an amount of bis-acrylamide which is about 1/5 times the amount of acrylamide has an average grain size of 23 nm. The two kinds of particles are shaped like spheres. The cation distribution is determined, from Co 2p 3/2 and Fe 2p 3/2 XPS spectra, to be (Co 0.4 Fe 0.6 )[Co 0.6 Fe 1.4 ]O 4 for both the samples, where (Co 0.4 Fe 0.6 ) and [Co 0.6 Fe 1.4 ] represent cations in the tetrahedral and octahedral sites, respectively. Magnetic measurement reveals a saturation magnetization of 67.3 A·m 2 ·kg ¹1 for sample S1 and 62.3 A·m 2 ·kg ¹1 for sample S2, but a similar coercivity of about 87.5 kA·m ¹1 for both the samples. [

Determination of the cation site distribution of the spinel in multiferroic CoFe 2 O 4 /BaTiO 3 layers by X-ray photoelectron spectroscopy

“…These values are close to the one found for CoFe 2 O 4 nanoparticles [10] (3 eV for Fe2p and 2.10 eV for Co2p), where the amount of normal spinel structure is higher than in our samples. Comparing our results with other experiments on similar samples can give discrepancies [24] since some do not take into account the Co 2p 1/2 peak or have not fitted the shake-up satellite. It so seems that taking into account all parameters -background, electronic levels 2p 3/2 and 2p 1/2 , shake-up satellites -is key in finding a unified method of XPS analysis.…”

“…Zhou et al [10] fit XPS spectra on bulk and powder CoFe 2 O 4 and differentiates Td and Oh sites, but do not use the same background as us for iron nor fit shake-up satellites. Wang et al [11] fit also Co and Fe with two peaks, and add the fitting of the shake-up satellite, but only consider the 2p 3/2 ion levels and not the 2p 1/2 as well. The following paragraphs detail our approach towards the exploitation of those XPS spectra.…”

“…Nevertheless, from previous reports no clear and reliable strategy for the XPS fitting procedure was established. It is still unclear how to correctly exploit XPS spectra to extract that data, especially considering that a given fitting method tends to have a non-negligible influence on the result, and methods seem to vary from paper to paper [10,11], sometimes leading to controversies [12,13]. The lack of direct comparison with XMCD does not allow to conclude on the pertinence of the proposed approaches.…”

Solvothermal synthesis of CoxFe3−xO4 spheres and their microwave absorption properties

“…Their spectral envelopes are composed of two main peaks, corresponding to 2p 3/2 and 2p 1/2 contributions. 43. 7(b), a shakeup satellite is observed between Fe2p 3/2 and Fe2p 1/2 peak in spheres C's spectrum, and spheres A and B have no satellites between them.…”

Cobalt-iron Oxide, Alloy and Nitride: Synthesis, Characterization and Application in Catalytic Peroxymonosulfate Activation for Orange II Degradation

“…Full XPS survey in Figure 6a shows the compositional information of the sample CFA-600, indicating the presence of Co, Fe, O, as well as C. The high-resolution XPS spectra of Co 2p, Fe 2p and O 1s are shown in Figure 6b-d, respectively. The Co 2p3/2 peaks at 779.5 eV and 781.5 eV were ascribed to Co 2+ at octahedral (B) and tetrahedral (A) sites of the spinel structure, respectively, with a satellite peak of Co 2p3/2 at ~785.5 eV [31]. There were also two peak signals for Fe 2p3/2 at 710.0 and 712.7 eV, suggesting the occupation of octahedral and tetrahedral sites, respectively.…”