Effect of Silica Embedding on the Structure, Morphology and Magnetic Behavior of (Zn0.6Mn0.4Fe2O4)δ/(SiO2)(100−δ) Nanoparticles

Abstract

The effect of SiO2 embedding on the obtaining of single-phase ferrites, as well as on the structure, morphology and magnetic properties of (Zn0.6Mn0.4Fe2O4)δ(SiO2)100−δ (δ = 0–100%) nanoparticles (NPs) synthesized by sol-gel method was assessed. The phase composition and crystallite size were investigated by X-ray diffraction (XRD), the chemical transformations were monitored by Fourier transform infrared (FT-IR) spectroscopy, while the morphology of the NPs by transmission electron microscopy (TEM). The average crystallite size was 5.3–27.0 nm at 400 °C, 13.7–31.1 nm at 700 °C and 33.4–49.1 nm at 1100 °C. The evolution of the saturation magnetization, coercivity and magnetic anisotropy as a function of the crystallite sizes were studied by vibrating sample magnetometry (VSM) technique. As expected, the SiO2 matrix shows diamagnetic behavior accompanied by the accidentally contribution of a small percent of ferromagnetic impurities. The Zn0.6Mn0.4Fe2O4 embedded in SiO2 exhibits superparamagnetic-like behavior, whereas the unembedded Zn0.6Mn0.4Fe2O4 behaves like a high-quality ferrimagnet. The preparation route has a significant effect on the particle sizes, which strongly influences the magnetic behavior of the NPs.

Sol-Gel Synthesis, Structure, Morphology and Magnetic Properties of Ni0.6Mn0.4Fe2O4 Nanoparticles Embedded in SiO2 Matrix

“…The Mn x Ni 1−x Fe 2 O 4 is isostructural with the two structures mentioned above, Ni and Mn being in the same position with an occupancy factor of x for Mn and 1−x for Ni. The reflection planes (220), (311), ( 222), (400), (422), (511) (440) and (533) belonging to the angular positions at 2θ = 29.99 or lack of SiO2 and the short time or calcination temperature required to produce pure crystalline Ni0.6Mn04Fe2O4 phase [5]. As the ferrite content decreases, in NCs with α = 25 and 50%, besides Ni0.6Mn04Fe2O4, the presence of α-Fe2O3 and Fe2SiO4 (JCPDS card no.…”

“…Manganese ferrite (MnFe 2 O 4 ) is of great interest due to its good biocompatibility, coloristic properties, tunable magnetic properties, guidability in a magnetic field and excellent chemical stability. MnFe 2 O 4 nanoparticles are also recognized as efficient agents for magnetic hyperthermia and magnetic resonance imaging [1][2][3][4][5]. MnFe 2 O 4 has a spinel crystal structure with Fe 3+ ions occupying the octahedral sites and Mn 2+ ions occupying the tetrahedral sites [4].…”

“…The sol-gel route is an easy way to produce ferrite-based NCs (nanocomposites) as it is a simple low-cost process and concedes the control of structure and properties [5]. The sol-gel method allows the production of nanosized composite materials containing highly dispersed magnetic ferrite particles [9].…”

“…For a better control of the particle size and particle agglomeration reduction, the coating of ferrite with silica (SiO 2 ) is often used. The SiO 2 coating also improves the magnetic properties and biocompatibility of the ferrites due to its bio-inert behavior in contact with living tissue [5]. Most of the organic surfactants reduce the biocompatibility due to their inflammatory reactions.…”

“…The SiO 2 layer cannot be solved or removed by the living tissue maintaining the optimal biocompatibility of the ferrite nanoparticles [10]. Tetraethyl orthosilicate (TEOS) is a network forming agent commonly used in the sol-gel synthesis, because it forms strong networks with moderate reactivity, permits the incorporation of various organic and inorganic molecules and offers short gelation time [5,11].…”