How shape and internal structure affect the magnetic properties of anisometric magnetite nanoparticles

Abstract

A three-step aqueous approach to obtain large (>50 nm) magnetite single-core particles has been developed. The steps are a) synthesis of antiferromagnetic nanoparticles, b) particle coating and c) subsequent reduction of the core material to magnetite. By variation of precursor material and process conditions, the synthesis yielded rhombohedra, discs or needles below 200 nm. A combination of X-ray diffraction, 57 Fe Mössbauer spectroscopy and infrared spectroscopy confirmed magnetite to be the dominant final core material. From transmission electron microscopy, we identified porous structures after the reduction. Magnetic characterization of the different magnetic nanopaticles revealed strikingly different magnetic behaviour depending on their shape, internal structure and reduction process. We conclude that each of these parameters have to be considered in further characterization of large magnetite nanoparticles.

Tailoring IONP shape and designing nanocomposite IONS@GN toward modification of SPCE to enhance electrochemical degradation of organic dye

“…Synthesis procedures for iron oxide nanocubes (IONC) and iron oxide nanoneedles (IONN) were described in references [45] and [46], respectively.…”

Anisotropic magnetic nanoparticles for biomedicine: bridging frequency separated AC-field controlled domains of actuation

“…14 The particle properties are those of magnetite, based on the suitability of iron oxides for biomedicine in comparison with other nanoparticles. 15 Particularly, as reference we have used disks of same dimensions and composition as those recently reported by H. Gavilán et al [16] obtained by dry reduction of an antiferromagnetic precursor, i.e. uniform magnetite particles of hexagonal shape with average dimensions 22 nm thickness and 140 nm diameter with a standard deviation of 10%.…”

“…Sketches illustrating the shape of the disks assumed in the BD simulations are shown in Figure 1, together with the TEM image of the experimental samples from reference [16], both the asprepared (A), and silica-coated (B) with smooth shapes. Importantly, those particles have a large in-plane magnetic moment, suitable for the BD description, as will be discussed later.…”

“…Importantly, those particles have a large in-plane magnetic moment, suitable for the BD description, as will be discussed later. 16 The scheme on the right aims to illustrate that the effect of the AC field is to promote physical reorientation.…”

“…The materials parameters are those of the magnetite (cubic anisotropy, K=-0.011×10 5 erg/cm 3 ; exchange stiffness A exch =1.0×10 -6 erg/cm), and the saturation magnetisation M S = 415 emu/cm 3 which was taken from Ref. [16].…”