MAGNETITE CRYSTAL-FORMATION FROM IRON(III) HYDROXIDE ACETATE - AN ELECTRON-SPIN-RESONANCE STUDY

Crystalline Fe//3O//4, magnetite, can be obtained by heating noncrystalline iron(III) hydroxide acetate (IHA). The inception of this amorphous-crystalline solid transformation was monitored by ESR spectroscopy, at various temperatures. No spectral changes are detected by heating samples for up to 2 h at temperatures below 190 degree C. Above this temperature the spectra change following a definite pattern: line widths increase at first and decrease at longer times until a steady value is reached; line-width decrease is faster at higher temperatures. ESR line intensities show little change at short heating times but they increase by 1 order of magnitude at longer times. ESR spectra allow the detection of two distinct events in IHA transformation to magnetite: the onset of ion mobility in the amorphous solid and (later) of magnetic ordering.