Crystal structures and magnetic properties of M2V2O7 (M=Co, Ni and Cu) compounds

The magnetic properties of M2V2O7 (M=Co, Ni and Cu) have been investigated between 4 and 300 K. The results emphasize the relationships between the structural and physical properties of the titled compounds. M2V2O7 (M=Co, Ni) exhibit a dichromate structure. The Ni-compound is antiferromagnetic, but the Co-one is ferromagnetic. Their specific heats confirm the low dimensionality at high temperature, and the magnetic transition is probably due to 3d–1d transition. The two varieties of Cu2V2O7 compounds are type thortveitite. α-Cu2V2O7 is an orthorhombic and β-Cu2V2O7 is a monoclinic. The β-Cu2V2O7 is an antiferromagnetic compound while α-Cu2V2O7 is appraised as a ferromagnetic or canted antiferromagnetic one.