TAYLOR et al, 1999. Spin-spin correlations in the insulating and metallic phases of the Mott system V2O3. European Physical Journal B, 12, pp. 199-207
The magnetic response in V2O3 has been investigated using polarised neutron scattering with
polarisation analysis. Measurements were carried out at three temperatures corresponding to the antiferromagnetic
insulating ground state, the metallic phase and the high temperature metallic phase. At the first
order metal insulator transition there is a dramatic change in the magnetic response with the metallic and
high temperature metallic phases being characterised by ferromagnetic spatial correlations of the paramagnetic
response. The establishment of ferromagnetic correlations at the metal insulator transition accounts
for the abrupt jump in the uniform susceptibility. It is proposed that the differentiation of the V-V distances
across the edges of VO6 octahedra is of critical importance for the change in electronic conductivity
but also for the establishment of the spatial correlations. The gradual high temperature evolution of the
conductivity then occurs by the reduction in the vanadium d overlap brought about by thermal expansion.
The first order reduction in atomic volume which occurs on the establishment of the metallic phase results
from an instability of the vanadium local moment arising from the change in electronic structure.
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