ESR study of the spin-Peierls transition in NaV2O5

ESR results are reported on the inorganic spin-Peierls compound alpha'-NaV2O5. A single crystal has been studied in the a-c plane perpendicular to the V4+O5 chains yielding a Lorentzian-shaped resonance absorption with g-values close to 2, characteristic for a spin-only system. The anisotropy of the g-values and the line width are studied in detail. The signal intensity vanishes exponentially below the spin-Peierls transition at T-SP = 33.5 K. At low temperatures in the dimerized state, the singlet-tripler gap amounts approximate to 100 +/- 2 K and the alternating exchange constants were determined to be J(1) = 500 K and J(2) = 619 K. (C) 1997 Elsevier Science Ltd.