Magnetic state of vanadium in chalcogenide V7Se8

The structural and magnetic properties of V7Se8 chalcogenide were studied using X-ray diffractometry, magnetic susceptibility measurements and nuclear magnetic resonance (NMR) spectroscopy on 51V nuclei. The ordering of vacancies in vanadium cationic layers with the formation of a 4C-type superstructure was found. It is estimated that the effective magnetic moment of vanadium ions is µeff = 0.35 µB. A significant local charge and magnetic heterogeneity of the V7Se8 compound has been revealed. The hyperfine interaction constant in vanadium ions is estimated from the temperature dependences of the magnetic shift of the NMR 51V line and the susceptibility χ(T) in V7Se8. A joint analysis of the NMR line shift data and the spin-lattice relaxation rate of 51V showed that the 3d-electrons of vanadium are in a itinerant state. At the same time, with decreasing temperature in the V7Se8 system, antiferromagnetic correlations are induced between the magnetic moments of vanadium in adjacent layers.