Related Experiment Video
Updated: Aug 7, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Correlation between spin-orbital coupling and the superparamagnetic properties in magnetite and cobalt ferrite spinel
1School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA.
Abstract:
The superparamagnetic properties of CoFe2O4 and Fe3O4 nanocrystals have been systematically investigated. The observed blocking temperature of CoFe2O4 nanocrystals is at least 100 deg higher than that of the same sized Fe3O4 nanocrystals. The coercivity of CoFe2O4 nanocrystals at 5 K is over 50 times higher than the same sized Fe3O4 nanocrystals. The drastic difference in superparamagnetic properties between the similar sized spherical CoFe2O4 and Fe3O4 (or FeFe2O4) spinel ferrite nanocrystals was correlated to the coupling strength between electron spin and orbital angular momentum (L-S) in magnetic cations. Compared to the Fe2+ ion, the effect of much stronger spin-orbital coupling at Co2+ lattice sites leads to a higher magnetic anisotropy and results in the dramatic discrepancy of superparamagnetic properties between CoFe2O4 and Fe3O4 nanocrystals. These results provide some insight to the fundamental understanding of the quantum origin of superparamagnetic properties. Furthermore, they suggest that it is possible to control the superparamagnetic properties through magnetic coupling at the atomic level in spinel ferrite nanocrystals for various applications.
Related Concept Videos
Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
Ferromagnetism
Valence Bond Theory
NMR Spectroscopy: Spin–Spin Coupling
Spin–Spin Coupling Constant: Overview
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Spin–Spin Coupling: One-Bond Coupling

