Abstract
Crystals of Na 4 [(Fe EDTA) 2 O]12H 2 O were investigated by means of electron paramagnetic resonance (EPR) spectroscopy. The spectra were obtained at various temperatures and crystals orientations. These spectra are very complex and have many absorption bands. The antiferromagnetic coupling between the iron atoms in the bridge Fe-O-Fe gives rise to states with total spin quantum number S=0, 1, 2, 3, 4, and 5. Analyses of the EPR spectra as a function of temperature permitted the identification of the EPR absorption lines. They were found to be due to the state with S=2. It was also possible to evaluate the exchange parameter as J≃202±10 cm -1 . From the study of the angular dependence of the absorption lines it was found that the magnetic axes X , Y , Z and the trial crystal axes a , b , c are related with a precision of 5°, by
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