No abstract

Spinel-type vanadium oxides have been studied from the viewpoints of spin and orbital order in a geometrically frustrated system. We have investigated the doping effects of Cr 3+ (3d 3 ) and Mo 3+ (4d 3 ), which have no orbital degrees of freedom, to the V 3+ (3d 2 ) site of MnV 2 O 4 , in order to clarify the structural, transport and optical properties of Cr-and Mo-doped samples. The orbital order is suppressed by Cr and Mo doping and the electronic structure depends on the doped elements. The results of transport and optics indicate that electrons are localized in the Cr-doped system, while they become nearly itinerant in the Mo-doped one.