Metal-Insulator Transitions in Pure and Doped V2O3

The addition of Ti³⁺ and Mg²⁺ to V₂O₃ leads to the suppression of the antiferromagnetic insulating phase; whereas the addition of Ti⁴⁺, Zr⁴⁺, and Fe³⁺ results in a first-order transition from a metallic to an insulating state. The effect of impurity ions is discussed in terms of the changes they cause in the bandwidth in analogy with the effect of pressure. The Hall coefficient of metallic V₂O₃ at 4.2 °K and 20 kbar is R_H=+(3.5+/-0.4)×10^-4 cm³/C which is close to the value measured at 150 °K and 1 atm. The residual resistivity of metallic V₂O₃ is strongly impurity dependent (140 μΩ cm/at.% Cr and 35 μΩ cm/at.% Ti). These results are not completely consistent with current theories for the metal-insulator transition in V₂O₃ but the best available model still seems to involve a localized-to-nonlocalized transition within the d band primarily involving orbitals in the basal plane.