Related Experiment Video
Updated: Jul 17, 2026
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
Spin incommensurability and two phase competition in cobaltites.
D Phelan1, Despina Louca, K Kamazawa
1Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA.
Physical Review Letters
|February 7, 2007
Summary
Strontium doping in lanthanum cobalt oxide (LaCoO3) induces a transition from insulator to ferromagnet. An incommensurate spin superstructure coexists with ferromagnetic clusters, impacting material properties.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid-State Chemistry
Background:
- LaCoO3 is a nonmagnetic Mott insulator.
- Sr2+ substitution for La3+ in La1-xSrxCoO3 leads to a spin cluster ferromagnetic (FM) state.
- Charge percolation through increasing spin clusters drives a metallic state.
Purpose of the Study:
- Investigate the magnetic phases in La1-xSrxCoO3 single crystals.
- Characterize the coexistence and competition between different magnetic structures.
- Understand the origin of residual resistivity in metallic samples.
Main Methods:
- Elastic neutron scattering on La1-xSrxCoO3 single crystals.
- Analysis of spin superstructures and ferromagnetic clusters.
- Correlation of magnetic properties with electrical transport.
Main Results:
- An incommensurate spin superstructure coexists with FM spin clusters.
- Incommensurability increases with Sr concentration (x).
- Spin incommensurability arises from local Co3+-Co4+ order, not long-range stripes.
Conclusions:
- The coexistence and competition between incommensurate and FM phases explain residual resistivity.
- Local cluster order, not long-range stripes, drives the incommensurate magnetism.
- Understanding these competing magnetic phases is crucial for La1-xSrxCoO3 applications.
Related Concept Videos
03:02Colors and Magnetism
Color in Coordination Complexes
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.
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.
02:42Valence 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...
01:20Spin–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...
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...
02:34Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
01:08Spin–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...
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...
01:31Ferromagnetism
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...