Magnetic anisotropy and spin fluctuations in the paramagnetic dimer [Fe(OMe)(ddpm)2]2:: Mossbauer spectroscopy and ab initio calculations

The magnetic anisotropy and the spin fluctuations of the paramagnetic molecule [Fe(OMe)(ddpm)(2)](2) are analyzed by means of Mossbauer spectroscopy in the temperature range [7.6 - 33] K. Spectra in the presence of a 5T magnetic field directed along the gamma rays were collected, by using a sample of pseudo-single crystal prepared by oriented grains. From the fits of the spectra, the hyperfine parameters are determined. Fits give also the value and direction of the magnetic anisotropy, referred to the electric field gradient (EFG) principal axes. The latter, together with the EFG components, were evaluated by means of ROHF ab initio calculations. Lastly, the rate of the spin transitions in function of T is discussed. (C) 2007 Elsevier B. V. All rights reserved.