Produção Nacional
Revisado por pares
Investigations on the structural and magnetic properties of Ba1-xGdxFe12O19 (0 ≤ x ≤ 0.15) nanoparticles
2022; Elsevier BV; Volume: 555; Linguagem: Inglês
10.1016/j.jmmm.2022.169340
ISSN1873-4766
AutoresM.A.P. Buzinaro, B. F. O. Costa, Maxim Ivanov, Graziele C. Cunha, M.A. Macêdo, Rômulo Simões Angélica, Nilson S. Ferreira,
Tópico(s)Magneto-Optical Properties and Applications
ResumoThe structural and magnetic properties of Ba1-xGdxFe12O19 (0 ≤ x ≤ 0.15) nanoparticles prepared using the proteic sol-gel process were investigated. Infrared spectroscopy, Raman spectroscopy, and X-ray powder diffraction measurements with Rietveld refinement analysis confirmed the formation of M-type BaFe12O19, whereas extra peaks of secondary phases were also detected for BaFeO3 (2θ = 28°), GdFeO3 (2θ = 38.4°), and Fe2O3 (2θ = 38.6°). Average crystallite size increases with Gd substitution in the range of 61–63 nm. Scanning electron microscopy revealed that the particle morphology of some samples consisted of a tendency for regular hexagonal platelets with inhomogeneous distribution of average grain size in the range of 250–280 nm. The room temperature magnetic studies revealed that considerable large saturation magnetization (Ms), remanence (Mr), and coercivity (Hc) for the Ba1-xGdxFe12O19 nanoparticles monotonically decreased to a minimum value until x = 0.1. However, it increased again to Ms ≈ 55.5 emu·g−1, Mr≈ 22.7 emu·g−1, and Hc ≈ 3.7 kOe for the x = 0.15 sample. The squareness ratio (SQR = Mr/Ms) values were lower than 0.5, illustrating the magnetic multidomain nature and uniaxial anisotropy of the samples. These results were investigated deeply with relation to hyperfine parameters and surface morphology of the samples by 57Fe Mössbauer spectroscopy and magnetic force microscopy (MFM). The hyperfine parameters indicated that the substitution of Gd3+ for Ba2+ induces exchange interactions in 2b-O2-4f2 and 12k-O2-2b, resulting in the higher magnetocrystalline anisotropy of the samples. Additionally, MFM images confirm that grain consisting of distributed smaller grains gives rise to a strip-and helix-like magnetic domain structure.
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