Synthesis process, size and composition effects of spherical Fe₃O₄ and FeO@Fe₃O₄ core/shell nanoparticles

Abstract

In this work, we study the link between synthesis conditions, crystalline structure and magnetic properties of exchange-coupled and single domain iron oxide nanoparticles

Strategies to tailor the architecture of dual Ag/Fe-oxide nano-heterocrystals—interfacial and morphology effects on the magnetic behavior

“…7(a)) and whose shape can be easily linked to a weakly interacting monodomain system [28,29]. The differences of Tm between the control sample and the more complex nanostructures can be explained considering three different phenomena: changes in the size of the magnetic nanoparticles [30], strengthening of dipolar interactions [31] and variations in the iron oxide phases [32]. However, for both Generally speaking, the Tm shift (as well as the ZFC/FC general curve shape) can be influenced by the morphology, metal seeds features and/or interface effects.…”

Large exchange bias in Cr substituted Fe3O4 nanoparticles with FeO subdomains

“…Moreover, being an interfacial phenomenon, the exchange anisotropy relies on a large AFM-FiM interface area to maximize the effect. Consequently, large EB is usually detected in CS systems with significant Fe x O volume fraction, and the effect is reduced with decreasing core size due to a reduced AFM-FiM interface area and AFM anisotropy 10,13,14 . The observed shift µ 0 H E = 460 mT is one of the highest values reported for a Feoxide NP system 18 and is quite remarkable given the small size and relatively low volume fraction of the Fe x O phase.…”

“…An extensively studied class of bimagnetic systems are Fe-oxide NPs composed of an AFM wüstite Fe x O core and a FiM magnetite Fe 3 O 4 shell 5,[10][11][12][13][14][15][16][17][18][19][20][21] . The most common approach for generating these systems is via thermal decomposition of Fe precursors, leading to metastable non-stoichiometric nano-crystalline Fe x O. Post-oxidation of the Fe x O nano-crystallites promotes diffusion and oxidation of Fe 2+ into Fe 3+ at the surface, leading to an inwards growth of the thermodynamically stable magnetite Fe 3 O 4 spinel phase and the formation of Fe x O-Fe 3 O 4 CS structures.…”

“…The most common approach for generating these systems is via thermal decomposition of Fe precursors, leading to metastable non-stoichiometric nano-crystalline Fe x O. Post-oxidation of the Fe x O nano-crystallites promotes diffusion and oxidation of Fe 2+ into Fe 3+ at the surface, leading to an inwards growth of the thermodynamically stable magnetite Fe 3 O 4 spinel phase and the formation of Fe x O-Fe 3 O 4 CS structures. Controlled post-synthesis treatment allows for varying the relative core-size dimensions, and studies have revealed a decreased coercivity and exchange-coupling with decreasing the size of the AFM phase due to a reduced AFM-FiM interface area and AFM anisotropy 10,13,14 . Moreover, post-synthesis thermal treatment can lead to oxidation-induced anti-phase domain boundaries and atomic-scale defects, resulting in anomalous magnetic properties and EB effects in single-phase Fe 3 O 4 NPs 11,22 .…”

Structure, morphology and magnetic properties of flowerlike γ-Fe2O3@NiO core/shell nanocomposites synthesized from different precursor concentrations

“…In addition, Gandha et al point out that the giant EB in Co/CoO core-shell nanowire assemblies has an angular dependence on the value of EB field and the direction of magnetization [13]. Recently, it has been reported that highly homogeneous and inverted core/shell magnetic nanocomposites which demonstrate significant EB effect can be synthesized by simple chemical methods, such as FeO/Fe 3 O 4 [14][15][16], CoO/γ-Fe 2 O 3 [17,18], MnO/γ-Mn 2 O 3 [19,20], and MnO/Mn 3 O 4 systems [20,21].…”