Correlation between magnetic spin structure and the three-dimensional geometry in chemically synthesized nanoscale magnetite rings

Abstract

The correlation between magnetic spin structure and geometry in nanoscale chemically synthesized Fe3O4 rings has been investigated by transmission electron microscopy. We find primarily the flux closure vortex states but in rings with thickness variations, an effective stray field occurs. Using tomography, we determine the complete three-dimensional geometries of thicker rings. A direct correlation between the geometry and the magnetization which points out of plane in the thickest parts of the ring yielding an intermediate magnetic state between the vortex state and the tube state is found. The interaction between exchange coupled rings leads to antiparallel vortex states and extended onion states.

Hydrothermal synthesis of α-Fe2O3 nanorings with the help of divalent metal cations, Mn2+, Cu2+, Zn2+ and Ni2+

“…a-Fe 2 O 3 particles could be easily converted to ferrimagnetic Fe 3 O 4 or c-Fe 2 O 3 particles under the hydrogen flow or in static hydrogen conditions at temperatures about 350°C [18]. The morphology of a-Fe 2 O 3 nanorings is perfectly preserved upon their conversion to Fe 3 O 4 or c-Fe 2 O 3 [8,16].…”

“…The magnetic nanoring possesses the vortex state characterized by a magnetic moment circulating around the ring [8,16]. In such a state magnetization turns out of the plane at the very centre of the vortex structure.…”

Driving large-velocity propagation of ferromagneticπ/2 domain walls in nanostripes of cubic-anisotropy materials

“…A quite big (estimated) value of the Gilbert damping constant of the Terfenol-D is a potential disadvantage that limits the DW velocity however. On the other hand, the brittleness of the Terfenol-D makes it difficult to process to the nanoscale, (while the nanotechnology of the magnetite is advanced [45]).…”

Three-dimensional characterization of stress corrosion cracks

“…However, it can also provide accurate crystallographic and chemical information. Both in TEM and STEM mode, it has been extensively applied to the characterization of complex systems which include studies of nanocomposites of FeAl + Y 2 O 3 , carbon nanotubes, Si particles embedded in SiO x , Pt catalysts nanoparticles, scanning tunnelling microscopy probes, polyhedral particles of CeO 2 , polymers, dislocations and magnetic rings [8][9][10][11][12][13][14][15], amongst others. In this paper, we use electron tomography to characterize crack tips in cold worked steels with complex microstructure.…”