Pressure-induced metal-insulator transition in the itinerant antiferromagnet Nb_12-xTi_xO₂₉ (x = 0 and 0.2)

We have carried out resistivity measurements on itinerant antiferromagnets Nb_12-xTi_xO₂₉ (x = 0 and 0.2) under pressure up to 2.5 GPa in order to investigate the pressure effects on these novel magnetic and metallic behaviors. The resistivity-temperature curves for both systems show metallic behavior at lower pressure, while the resistivity increases with decreasing temperature at higher pressure. These results indicate that a metal-insulator transition is induced by the application of the pressure in both systems. We will discuss the origin of the metal-insulator transition in terms of charge ordering and pressure-induced amorphization as have been suggested in other niobium oxides.