Spin dynamics of the magnetic dimer [Fe(OMe)(dpm)_{2}]_{2} studied using Mössbauer spectroscopy
Abstract
We present a study of the spin dynamics of the magnetic dimer [Fe(OMe)(dpm)_{2}]_{2}, using Mössbauer spectroscopy. In this cluster, the two iron(III) ions are antiferromagnetically coupled so that the dimer presents a S=0 spin ground state. Spin multiplets with values of S ranging from 1 to 5 follow in order of increasing energy. Axial anisotropy DS^{2}_{z} is also present with D of the order of a few kelvin. Spectra were collected over a range from 6.5 K to room temperature. They consist of doublets in which any magnetic structure is lacking, but the line widths of which increase with the temperature, due to relaxation effects. We performed their fits by assuming a fastfluctuating hyperfine field which stochastically inverts its direction along the anisotropy axis. The zerofrequency Fourier transform J_{z} of the hyperfinefield correlation function versus the temperature was obtained from the spectrum fittings. The trend of J_{z} suggests that the basic mechanisms of the spin dynamics consist of a tunnel effect due to magneticanisotropy transversal terms, as well as of spinthermal bath interactions. By assuming this, the following parameters were estimated from the fitting of J_{z}(T): D(1)≈8.1 K, E/D(1)≈8.5×10^{4}, and w=w_{0}exp(2T_{0}/T) with w_{0}≈9.2×10^{8} s^{1} and T_{0}≈732 K. Lastly, similarities in spin dynamics between the dimer and the ring shaped clusters were discussed.
 Publication:

Physical Review B
 Pub Date:
 January 2004
 DOI:
 10.1103/PhysRevB.69.014418
 Bibcode:
 2004PhRvB..69a4418C
 Keywords:

 67.57.Lm;
 61.46.+w;
 87.64.Pj;
 Spin dynamics;
 Mossbauer spectroscopy