Mössbauer studies of electron spin relaxation and radiolytic effects in diluted tris(acetylacetonato) FeIII

Abstract

The Mössbauer spectra of tris(acetylacetonato)iron(III), [Fe(AcAc)₃] diluted in tris(acetylacetonato)aluminium(III), [Al(AcAc)₃] and tris(acetylacetonato)gallium(III), [Ga(AcAc)₃] have been obtained at room temperature and 110 K. The linewidth broadening observed in these spectra is temperature and concentration dependent. This line broadening phenomenon is attributed to paramagnetic spin relaxation. The resolved hyperfine structures at 4.2 K for the 1 wt % Fe(AcAc)₃ in (Fe.Al)(AcAc)₃ sample are consistent with this interpretation.

Irradiation of the diluted Fe(AcAc)₃ samples with ⁶⁰Co γ rays at room temperature leads to a decrease in the Fe(AcAc)₃ Mössbauer line widths, and Fe^II peaks at low Fe(AcAc)₃ concentrations in the Al(AcAc)₃ matrix. These observations are consistent with a motional narrowing mechanism proposed earlier. The results are discussed in terms of an effective radiolytic mechanism simulated by external radiation.