Delafossite oxides containing vanadium(III): Preparation and magnetic properties

Although the pure delafossite CuVO2 does not exist, the present study well confirms that large amounts of vanadium(III) can be incorporated into copper based delafossites without reducing Cu+ into metallic copper, as several solid solutions CuM1−xVxO2 exist where M=Ga, Cr (x⩽0.50) or Fe (x⩽0.67).Vanadium(III) has a peculiar magnetic behavior. Actually VV antiferromagnetic interactions appear rather large at high temperature, but as the temperature decreases magnetic data can be (at least qualitatively) interpreted assuming the formation of VV pairs. The bonding involves one of the two electrons of the 3d2 (a11e1) configuration of V(III)-atoms having a 6-fold D3d coordination, the one occupying the e orbital that lies in the (M, V) layers of the delafossite structure. The behavior changes from a rather 2D ferrimagnetic-like one to a 3D antiferromagnetic one with a Néel temperature larger than 4.5 K in the case of CuFe1−xVxO2 as determined from a Mössbauer study.