Magnetic Resonance Studies of the Quasi-One-Dimensional Conductor α'–NaxV2O5

We present the EPR and NMR results on the quasi-one-dimensional conductor α'-Na x V 2 O 5 ( x =1.0, 0.9 and 0.78) in the temperature range from 12 K to 397 K. The spin susceptibility extracted from EPR measurements has a broad maximum around room temperature. The 51 V NMR line shift associated with the V 4+ ion increases with decreasing temperature below room temperature. The ground state of the V 4+ ion is spin-singlet and it is understood as bipolaronic state, which is the electron pairs of the adjacent V 4+ ions formed by the strong electron-phonon interaction. In the case of x =1.0, it is pointed out that there are the vanadium zigzag chains occupied by the only V 4+ ions, where the electron wave function overlaps directly.