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Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene
Published on: July 3, 2015
Charge-order-driven spin-peierls transition in alpha(')-NaxV2O5
Fagot-Revurat1, Mehring, Kremer
1Physikalisches Institut, Universitat Stuttgart, 70550 Stuttgart, Germany.
Physical Review Letters
|September 16, 2000
Summary
Sodium vanadium oxide (Na_xV_2O_5) exhibits a charge-ordering transition below 37 K, preceding lattice distortion. A spin gap forms at 34.7 K, indicating unique charge density wave and spin-Peierls order in this 1/4-filled ladder system.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid-State Chemistry
Background:
- Alpha-phase sodium vanadium oxides (α-Na_xV_2O_5) are 1/4-filled inorganic spin chains with complex magnetic and structural properties.
- Understanding the interplay between charge, spin, and lattice degrees of freedom is crucial for novel electronic materials.
Purpose of the Study:
- To investigate the low-temperature phase transitions in α-Na_xV_2O_5 (x = 0.996).
- To elucidate the nature of the transition involving charge ordering, lattice distortion, and spin gap formation.
Main Methods:
- Utilizing 23Na and 51V Nuclear Magnetic Resonance (NMR) spectroscopy.
- Analyzing temperature-dependent NMR spectra to probe local electronic and structural environments.
Main Results:
- A charge-ordering transition was identified starting at or below 37 K, occurring before lattice distortion.
- A spin gap (Δ = 106 K) was observed to form at the critical temperature (T_c) of 34.7 K.
- Below T_c, the 23Na NMR signal split into eight distinct quadrupolar lines, indicating significant lattice distortion and unit cell doubling in the (a,b) plane.
Conclusions:
- The observed transition in α-Na_xV_2O_5 involves coupled charge density wave and spin-Peierls ordering.
- The NMR data provide strong evidence for a complex, unique transition mechanism in this 1/4-filled ladder system.
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