Tetragonal and cubic CuFe2O4 are prepared and studied by Mössbauer‐effect technique at room temperature and at 4.2 K with and without applied strong magnetic fields. The cation distributions and the hyperfine parameters are determined and compared with magnetization measurements. The results show that tetragonal CuFe2O4 is an inverse spinel of Néel collinear arrangement of spins and that cubic copper ferrite is not completely inverse with a cation distribution dependent on the heat treatment.

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[II] have been chosen for EPR study. This study is a continuation of our recent investigation related to solid gadolinium complexes: β-diketonates and aminopolycarboxylates. The EPR spectra of the Gd-polyoxometalates studied provide much better resolution than those recently studied. The spectra of Gd-polyoxometalates containing 1.7 to 2.5% of Gd(HI) do not require an additional computer processinng for correct interpretation. It is on tle contrary to the β-diketonates and polyamieocarboxylates (witl the content of Gd(III) 22-33%) for which the use of the RKU computer program (based on Fourier transform) was necessary in .order to enhance the spectra resolution thus improving their correct interpretation. Tle EPR spectra obtained for the compounds Ι and II markedly differ from the U-spectrum characteristic of Gd(HI) in glasses. Taking into account the spin-Hamiltonian calculations the existence of Gd(III) ion in two different surroundings: in a strong crystal freld of rhombic symmetry and in a weak crystal field, is observed. The differences observed between the case I and II seem to be related to a various hydration degree.