Mapping magnetic fields of Fe3O4 nanosphere assemblies by electron holography

Abstract

Crystalline Fe3O4 nanospheres with averaged diameters of 150 nm have been synthesized by a facile solvothermal method and characterized using transmission electron microscopy and electron holography. The nanospheres can self-assemble into either chain-like or ring-like shapes with sizes of a few micrometers, where large magnetic moments are found for individual particles at the remanent state and lead to strong fringing field in vicinity of the assemblies. Magnetic dipolar moments can be aligned both within and out of the sample plane, with a typical length scale on the order of 500 nm.

Dependency of magnetic microwave absorption on surface architecture of Co20Ni80hierarchical structures studied by electron holography

“…4a. 42,43 Here, we illustrate the application of electron holography to the characterization of the magnetic properties of Co 20 Ni 80 alloy on nanometer scale. It is well known that the CTAB molecules could behave as soft templates for transition metal compound.…”

“…Electron holography analysis has been applied on a wide variety of materials such as quantum wells, magnetic thin films, semiconductor devices and natural rocks. 42,43 Here, we illustrate the application of electron holography for the characterization of the magnetic properties of Co 20 Ni 80 alloys on a nanometer scale.…”

Size-Specific Spin Configurations in Single Iron Nanomagnet: From Flower to Exotic Vortices

“…In these contexts, one needs to evidence at room temperature the single-domain limit separating SD and V states. The determination of this single-domain limit in a single nanoparticle has been largely investigated numerically and is predicted to be in the order of several exchange lengths, that is, from 15 to 25 nm depending of the material. − Though spin configurations were experimentally determined in different nanomagnets such as nanowires, ,, nanocubes, , nanospheres, − faceted nanoparticles, or nanorings, , no result has been reported on the experimental determination of the critical size, even for nano-objects with the simplest geometries. This is mainly due to the limited sensitivity and resolution of existing experimental techniques, which do not allow studying isolated nanomagnets of size close to the expected transition.…”

TEM and Associated Techniques

“…However, observed in this manner, a pattern formed by the suspended iron oxide nanoparticles can be misleading in terms of the actual particle self-organization and the resultant geometries of the particle assemblies, both dependent on the solvent coordination. Moreover, solvent evaporation can contribute to unwanted aggregation of the deposited nanoparticles, further complicating the analysis [97,103,106].…”