Magnetic and electronic properties of hexairon(III) nanocluster with cyclic structure: a Mossbauer study

A molecular cluster containing a coplanar ring of iron(III) ions with spin 5/2 was investigated by Mossbauer spectroscopy. The iron spins are antiferr omagnetically coupled so that the ground state has total spin S = 0. Spectr a in the absence of an applied magnetic field consisted of a quadrupolar do ublet, the linewidth of which monotonically increased with the temperature. A quadrupolar splitting of about 0.35 mm/s was found. Calculations of the iron-orbital electronic populations were carried out and the quadrupolar sp litting was estimated. Its value was in agreement with the experimental one . In addition, the trend of the linewidth was explained in terms of isotrop ic spin fluctuations. Spectra in the presence of a 4.5 T longitudinal magne tic held were also collected. The hyperfine field was obtained from their f itting. Differences with respect to the hyperfine field obtained from susce ptibility data were also interpreted in terms of spin fluctuations.