L. Cianchi

Phonon field contribution to the g shift in Yb+3: YES

Abstract The dynamic crystal field correction to the g factor of Yb +3 : YES is evaluated. The approach is through the normal modes of the compex. It is found that the zero point phonon field contribution is in agreement with the observed g shift.

Isotropic relaxation of the hyperfine field and intercluster interactions in ferrihydrite

A theory for the fluctuations of the magnetic moment of the grains in ferrihydrite is developed, and their influence on the Mossbauer spectra is studied in the range of temperatures between 26 K and 65 K. The evolution of the spectra can be interpreted in terms of isotropic relaxation, in spite of the fact that they are not ordinary relaxation spectra. The results make it clear that superferromagnetic relaxation is present.

The deoxygenation process in oxyhemoglobin and the role of the Jahn Teller effect

Abstract In this letter it is shown that, since in HbO2 the local symmetry cannot be greater than C4v, the J.T. effect can be discarded as the mechanism leading to the removal of O2 molecule.

Relaxation effects in Fe17 and Fe19 oxo-bridged iron clusters

The magnetic properties of a new type of iron clusters are studied by means of Mössbauer spectroscopy in an applied magnetic field. The results obtained agree with the ones obtained from magnetic susceptibility measurements. They are well explained in terms of relaxation determined by fluctuations in the hyperfine field due to spin-spin interaction. The triangular arrangement of the iron ions plays an essential role in this mechanism giving rise to spin frustration effects.

Mössbauer spectra of EuPd3B0.5, an experimental test of a microscopic theory

The Mössbauer spectra of EuPd3B0.5 have been interpreted on the basis of the general microscopic theory previously developed by the authors. The theory connects the valence state of the europium ion with the distribution of the neighbouring boron atoms. The general characteristics of the present spectra are fairly well accounted for by theory, and an evolution with temperature of the line intensity ratio, in good agreement with the experimental data, is predicted.

On the temperature dependence of the g shift in Nd3+:YES

Abstract A temperature-dependent contribution to the g factor of Nd 3+ :YES has been observed. A semi-empirical theory of the phenomena is presented in which the matrix elements of the dynamic crystal field potential are evaluated starting from spin-lattice relaxation rates. The evaluated contribution is in good agreement with the observed g shift.

A comment on the evaluation of E.F.G. tensor components in HbO2

Abstract It is shown that the discrepancy between the evaluated E.F.G. tensor components in the Griffiths model and the experimental ones is erroneus. It arises only from the choice of two different reference frames.