Abstract
The structure, morphology and magnetic properties of (Ni0.6Mn0.4Fe2O4)α(SiO2)100−α (α = 0–100%) nanocomposites (NCs) produced by sol-gel synthesis were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). At low calcination temperatures (300 °C), poorly crystallized Ni0.6Mn0.4Fe2O4, while at high calcination temperatures, well-crystallized Ni0.6Mn0.4Fe2O4 was obtained along with α-Fe2O3, quartz, cristobalite or iron silicate secondary phase, depending on the Ni0.6Mn0.4Fe2O4 content in the NCs. The average crystallite size increases from 2.6 to 74.5 nm with the increase of calcination temperature and ferrite content embedded in the SiO2 matrix. The saturation magnetization (Ms) enhances from 2.5 to 80.5 emu/g, the remanent magnetization (MR) from 0.68 to 12.6 emu/g and the coercive field (HC) from 126 to 260 Oe with increasing of Ni0.6Mn0.4Fe2O4 content in the NCs. The SiO2 matrix has a diamagnetic behavior with a minor ferromagnetic fraction, Ni0.6Mn0.4Fe2O4 embedded in SiO2 matrix displays superparamagnetic behavior, while unembedded Ni0.6Mn0.4Fe2O4 has a high-quality ferromagnetic behavior.
Highlights
This study investigates the influence of the mixed Ni-Mn ferrite embedding in various contents of amorphous SiO2 matrix, at different calcination temperatures on the structure, morphology and magnetic properties of (Ni0.6 Mn04 Fe2 O4 )α (SiO2 )100−α NCs using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM)
In the absence of an SiO2 matrix (α = 100%), single-phase crystalline Ni0.6 Mn0.4 Fe2 O4 was obtained at 300 ◦ C, while at 700 and 1100 ◦ C, ferrite is accompanied by an α-Fe2 O3 secondary phase
Ni0.6 Mn0.4 Fe2 O4 is formed at 300 ◦ C, α-Fe2 O3 and Fe2 SiO4 secondary phases accompany the Ni0.6 Mn0.4 Fe2 O4 at 700 ◦ C, while at 1100 ◦ C Ni0.6 Mn0.4 Fe2 O4 is accompanied by quartz and cristobalite
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. At calcination temperatures above 900 ◦ C, a part of the Mn2+ ions migrate from tetrahedral (A) to octahedral (B) sites leading to a mixed spinel structure [4,6]. The ferrite structure and magnetic properties are sensitive to synthesis methods, additive substitutions and calcination process [8]. This study investigates the influence of the mixed Ni-Mn ferrite embedding in various contents of amorphous SiO2 matrix, at different calcination temperatures on the structure, morphology and magnetic properties of (Ni0.6 Mn04 Fe2 O4 )α (SiO2 )100−α NCs using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM)
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