In orthorhombic Nb12O29 reported as the first example of a magnetically ordered ( TN = 12 K) system in niobium-based oxides, the metallic conduction even below TN suggests that Nb12O29 could be an itinerant antiferromagnet. In order to investigate the pressure effects on these novel magnetic and metallic behaviors, we have carried out resistivity measurements up to 2.5 GPa. The resistivity-temperature curves show metallic behavior below Pc ∼ 1 GPa. On the other hand, when pressure is applied over ∼1 GPa, the resistivity increases with decreasing temperature from 300 K. These results indicate metal-insulator (MI) transition at Pc ∼ 1 GPa. We will discuss the origin of the MI transition in Nb12O29 in terms of charge ordering and pressure-induced amorphization as have been suggested in other niobium oxides.
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