Magnetic and structural properties of stoichiometric and non-stoichiometric (V,Al)O2alloys

Abstract
The structural and magnetic properties of the system V1-xAlxO2+or-y have been investigated by X-ray diffraction, NMR, magnetic susceptibility and EPR measurements. The existence of two insulating intermediate phases M2 and T between the insulating M1 and the metallic R is confirmed. The effect of oxygen non-stoichiometry is studied; it is shown that an excess of oxygen increases the stability of the M2 phase. The susceptibility of the M2 phase is that of a linear antiferromagnetic Heisenberg chain with J=-390K, due to the localised V4+ ions. The M2 to T transition corresponds to the dimerisation of the chains. This article confirms the results obtained for the system V1-xCrxO2 and their interpretation.