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Related Concept Videos

NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
¹H NMR Signal Multiplicity: Splitting Patterns01:13

¹H NMR Signal Multiplicity: Splitting Patterns

When protons A and X are coupled, their nuclear spin energy levels are slightly modified. This is because the energy required to excite proton A to a spin state parallel to proton X is slightly different from the energy required for it to become anti-parallel to spin X. Consequently, there are two possible excitation frequencies for A (A1 and A2), depending on the spin state of X, and vice versa. The mutual nature of coupling implies that the difference between frequencies A1 and A2, indicated...

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Related Experiment Video

Updated: Jun 3, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
08:55

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Published on: June 7, 2018

Interface exchange coupling in Co nanoparticles dispersed in a Mn matrix.

C Binns1, N Domingo, A M Testa

  • 1Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK. cb12@le.ac.uk

Journal of Physics. Condensed Matter : an Institute of Physics Journal
|March 16, 2011
PubMed
Summary

This study reveals that cobalt-manganese (CoMn) alloy nanoparticles exhibit a core-shell structure with a ferromagnetic cobalt-rich core and an antiferromagnetic manganese-rich shell, leading to exchange bias effects.

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08:40

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

Published on: December 6, 2021

Area of Science:

  • Materials Science
  • Nanotechnology
  • Condensed Matter Physics

Background:

  • Understanding the magnetic properties of alloy nanoparticles is crucial for developing advanced magnetic materials.
  • Cobalt (Co) and Manganese (Mn) alloys are of interest due to their unique magnetic behaviors.

Purpose of the Study:

  • To investigate the structural and magnetic properties of cobalt nanoparticles dispersed in a manganese matrix.
  • To elucidate the formation of core-shell structures and their influence on magnetic behavior.

Main Methods:

  • Co-deposition of pre-formed Co clusters with Mn vapor.
  • Characterization using Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Magnetic Circular Dichroism (XMCD).
  • Magnetic property analysis via magnetometry and theoretical modeling (Monte Carlo simulations, electronic structure calculations).

Main Results:

  • Formation of CoMn alloy core-shell nanoparticles with a Co-rich ferromagnetic core and Mn-rich antiferromagnetic shell at low Co volume fraction.
  • Significantly reduced Co magnetic moment within the core compared to Co nanoparticles in Ag.
  • Observation and replication of low-temperature exchange bias (EB) behavior.

Conclusions:

  • Alloying significantly influences the magnetic moment of Co atoms in the core.
  • Exchange bias arises from the interaction between the ferromagnetic Co-rich core and the antiferromagnetic Mn-rich shell.
  • The core-shell structure and resulting exchange bias are key features of these Co@Mn nanoparticles.