On the magnetic properties of Lithium Vanadium Bronzes Li x V 2 O 5

Magnetic susceptibility of V 2 O 5 and of the α‐, ϵ‐, δ‐ and γ‐Li x V 2 O 5 bronzes prepared either at high or at room temperature has been measured between liquid helium and ambient temperature. The results are representative of the localized character of the V 4+ ion d‐electron and, for high enough x‐values, of the existence of antiferromagnetic interactions in a low dimensional system. The intrachain exchange integral J has been determined using the Bonner / Fischer model for Heisenberg chains with S = 1/2 spin. It is larger for the γ‐ than for the δ‐phase. This result as well as the occurrence of long range ordering below T N ≈ 130 K in the γ‐phase may be ascribed to ordering of V 4+ and V 5+ ions in the former bronze and to the random distribution of V 4+ ions in the latter one.