FLUOROCOMPLEXES OF NIOBIUM .4. THE MAGNETIC-STRUCTURE OF VNBF6

X-ray and neutron diffraction experiments performed on the compound (V NbF6)-Nb-II-F-IV have shown that it crystallizes in the rhombohedral s ystem, space group R $($) over bar$$ 3, with a cationic ordering. Its ferrimagnetic behaviour (T-c approximate to 35 K) is studied from the thermal variation of the molar susceptibility, magnetization measureme nts and neutron powder diffraction data. Both magnetic and nuclear cel ls are identical and the magnetic moments (mu(V2+)=2.44 mu(B) and mu(N b)(4+)=0.34(mu B) at 1.4 K) lie along the c-axis of the hexagonal cell .