VANADATE FAMILY AS SPIN-GAP SYSTEMS

Authors
Citation
Y. Ueda, VANADATE FAMILY AS SPIN-GAP SYSTEMS, Chemistry of materials, 10(10), 1998, pp. 2653-2664
Citations number
53
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Chemistry Physical","Material Science
Journal title
ISSN journal
0897-4756
Volume
10
Issue
10
Year of publication
1998
Pages
2653 - 2664
Database
ISI
SICI code
0897-4756(1998)10:10<2653:VFASS>2.0.ZU;2-8
Abstract
The structural and magnetic properties of the vanadate family with the chemical formula AV(2)O(5) (A = Li, Na, Cs, Mg, and Ca) are reviewed in terms of low-dimensional quantum-spin systems. These compounds have layered structures with A cations lying between layers. A structural element common to them is a VO5 square pyramid formed by five oxygens surrounding the V ion. Each compound has a structure with a characteri stic arrangement of VO5 square pyramids formed by the sharing of edges and/or corners. All of these compounds are low-dimensional, spin-1/2 magnets and are spin-gap systems except gamma-LiV2O5. alpha'-NaV2O5, i s a spin-Peierls system with the transition temperature T-SP = 35 K an d the energy gap Delta = 114 K. The parameter 2 Delta/k(B)T(SP) = 3.53 holds well for the all organic and inorganic spin-Peierls compounds e xcept alpha'-NaV2O5 for which the measure is 6.44. This difference sug gests that the transition observed in alpha'-NaV2O5 is not a conventio nal spin-Peierls transition but an exotic one. Both MgV2O5 and CaV2O5 are spin-ladder systems with a similar two-leg ladder structure but th e gap energy (similar to 17 K) observed in MgV2O5 is very small compar ed with that (similar to 600 K) in CaV2O5. CsV2O5 is a dimer system wi th a spin gap of similar to 160 K. gamma-LiV2O5, which has one-dimensi onal zigzag chains in the structure, shows neither spin gap nor magnet ic order down to 0.5 K.