  The spinel FeV2O4 is known to exhibit peculiar physical properties, which is
generally ascribed to the unusual presence of two cations showing a pronounced
interplay between spin, orbital and lattice degrees of freedom (Fe2+ and V3+ on
the tetrahedral and octahedral sites, respectively). The present work reports
on an experimental re-investigation of this material based on a broad
combination of techniques, including x-ray diffraction, energy dispersive and
M\"ossbauer spectroscopies, as well as magnetization, heat capacity, dielectric
and polarization measurements. Special attention was firstly paid to establish
the exact cationic composition of the investigated samples, which was found to
be Fe1.18V1.82O4. All the physical properties were found to point out a complex
ordering process with a structural transition at TS = 138 K, followed by two
successive magnetostructural transitions at TN1 = 111 K and TN2 = 56 K. This
latter transition marking the appearance of electric polarization,
magnetization data were analysed in details to discuss the nature of the
magnetic state at T< TN2. An overall interpretation of the sequence of
transitions was proposed, taking into account two spin couplings, as well as
the Jahn-Teller effects and the mechanism of spin-orbit stabilization. Finally,
the origin of ferroelectricity in Fe1.18V1.82O4 is discussed on the basis of
recent models.
