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Related Concept Videos

Ferromagnetism01:31

Ferromagnetism

Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
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: 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,...
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
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...
Valence Bond Theory02:42

Valence Bond Theory

Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
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...

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Related Experiment Video

Updated: Jul 6, 2026

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope
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Spin tunneling in junctions with disordered ferromagnets.

P V Paluskar1, J J Attema, G A de Wijs

  • 1Department of Applied Physics, cNM, Eindhoven University of Technology, The Netherlands. p.v.paluskar@tue.nl

Physical Review Letters
|March 21, 2008
PubMed
Summary

Amorphous CoFeB exhibits higher tunneling spin polarization (TSP) than crystalline fcc CoFeB. This finding, supported by electronic structure calculations, advances understanding of spin transport in complex magnetic materials.

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Area of Science:

  • Condensed Matter Physics
  • Materials Science
  • Spintronics

Background:

  • Tunneling spin polarization (TSP) is crucial for spintronic devices.
  • Understanding the influence of material structure on TSP is essential for device optimization.
  • Cobalt-Iron-Boron (CoFeB) alloys are widely used in magnetic tunnel junctions.

Purpose of the Study:

  • To compare the tunneling spin polarization (TSP) of amorphous CoFeB with that of face-centered cubic (fcc) CoFeB.
  • To elucidate the atomic and electronic structure contributions to TSP in these materials.
  • To validate theoretical predictions against experimental measurements.

Main Methods:

  • First-principles atomic and electronic structure calculations.
  • Experimental measurement of tunneling spin polarization.
  • Analysis of s-electron spin polarization contributions.

Main Results:

  • Amorphous CoFeB demonstrates significantly higher TSP compared to fcc CoFeB.
  • Calculated s-electron spin polarization shows excellent agreement with measured TSP.
  • The disordered structure of amorphous CoFeB plays a key role in its enhanced spin polarization.

Conclusions:

  • The study provides compelling evidence that amorphous CoFeB is superior to fcc CoFeB in terms of TSP.
  • The findings reinforce the understanding of tunneling phenomena in AlO(x) based magnetic tunnel junctions.
  • Key factors influencing spin polarization in complex ternary alloys are highlighted for future research.