Probing the Size Effect of Co₂FeGa-SiO₂@C Nanocomposite Particles Prepared by a Chemical Approach

Abstract

In this contribution, we report the chemical synthesis of carbon coated, silica supported Co2FeGa (Co2FeGa-SiO2@C) nanocomposite particles. The particle size of Co2FeGa particles can be tuned by varying the amount of silica supports. The dependences of the crystal structure and magnetic properties on particle size have been investigated by synchrotron radiation based X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, transmission electron microscope (TEM), 57Fe Mössbauer spectroscopy, and superconducting quantum interference device (SQUID). The superparamagnetic critical size of Co2FeGa Heusler nanoparticles is found to be ∼17 nm by correlating the TEM derived particle size distribution to the Mössbauer spectroscopy data. The effects of silica supports and carbon coating on the formation of Co2FeGa nanoparticles of various sizes are also discussed.

Nanocrystalline alloys: synthesis and characterization of non-stoichiometric Co2FeAl nanocrystals

“…20 It is worth noting that in all these reports [8][9][10][11] (as is the case here) the compound is non-stoichiometric and departs to varying degrees from the nominal Co 2 FeAl composition. Finally, Philip and coworkers reported on the preparation of Co 2 FeAl nanowires via an electrospinning route.…”

“…6,7 While ternary alloys have been extensively studied in the bulk and thin-film forms, [1][2][3] to date cobalt-based nanocrystalline ternary alloys have only received limited attention. [8][9][10][11][12] Nanocrystalline alloys can be used as the active layer in, for example, granular magnetoresistance devices; [13][14][15][16] while such devices are not as performing as fully epitaxial multilayered thin-film stacks, 17 they greatly benefit from ease of processing and greatly lowered cost.…”

Synthesis, characterization and magnetic properties of hollow Co2FeAl nanoparticles: the effects of heating rate

“…These differences in the magnetic properties of the Co 2 FeAl HNPs may arise from the SP effects in magnetic NPs due to the decrease in the NP/crystallite size, 28 According to the literature, the magnetic properties of Co-based Heusler NPs such as Co 2 FeGa and Co 2 NiGa have been investigated. 25 25 To further study the magnetic properties of the HNPs, we have performed FORC analysis which will be discussed in the next section.…”

“…54 The FORC analysis also reveals the formation of a mixture of SP and SD grains, where the SD contribution is dominant. Correlating TEM-derived NP size distribution and Mössbauer spectroscopy data, Wang et al 25 proposed an alternative approach to estimate the SP critical size of Co 2 FeGa Heusler NPs with broad size distribution. In this case, the SP size of Co 2 FeGa NPs was found to be approximately 17 nm, which is reasonably close to that of FeCo NPs and Co 2 FeAl HNPs indicated earlier.…”

“…23 Additionally, by reducing a methanol impregnated mixture of Co, Fe and Ga precursors, Co 2 FeGa Heusler NPs were synthesized after loading on fumed silica, followed by heating the dried samples under pure H 2 atmosphere at 900 °C. 24,25 In order to carefully study the magnetic processes in a variety of magnetic nanostructured materials including nanowires, nanotubes, nanoholes and NPs, the use of firstorder reversal curve (FORC) analysis based on the classical and/or moving Preisach models has proven to be promising. [26][27][28][29] For describing weakly interacting systems (e.g., magnetic NPs), the use of the classical model is superior to the moving model.…”