ISSN:
0084-6600
Source:
Annual Reviews Electronic Back Volume Collection 1932-2001ff
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Jahn-Teller phenomena encountered in oxides are reviewed briefly. High-spin Mn(III) in an octahedral site illustrates an ion with twofold orbitally degenerate sigma-bonding orbitals having a quenched orbital angular momentum; octahedral V(III) and high-spin Co(II), as well as tetrahedral high-spin Ni(II), are examples of ions with threefold orbitally degenerate pi-bonding orbitals that retain orbital angular momentum. Cooperative local deformations that are static give rise, below a transition temperature Tt, to a lowering of the lattice symmetry, anisotropic interactions, and the possibility of a ferromagnetism that is oriented in opposition to a magnetic field applied on cooling through the transition. Dynamic local deformations can influence the physical properties of a solid in a variety of ways. Of special interest is the influence of dynamic deformations at a cross-over from localized to itinerant electronic behavior in a mixed-valent system.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1146/annurev.matsci.28.1.1
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