JAHN-TELLER DISTORTION - MAGNETIC STUDIES OF VANADIUM TETRACHLORIDE

Paramagnetic resonance of polycrystalline VCU diluted with TiCli has been observed near 9, 24, and 36 GHz below 9°K. Both g values and hyperfine A tensors are axially symmetric and temperature independent with the same principal axes :g∥ = 1.920, g⊥ = 1.899, |A∥|= 12 G, |A⊥| = 120G. The average g value obtained from susceptibility data is in agreement with the resonance value. The paramagnetic relaxation time T1 varies with temperature as shown by the relation T1 = 2×10-9 exp(25/T) sec, indicating the presence of a potential barrier approximately 18 cm-1 in height. The results indicate a static Jahn-Teller distortion, but with large zero-point vibrations. This situation is in between Ballhausen-de Heer's ligand field and Ballhausen-Liehr's crystal-field calculations.