Abstract
The Mossbauer spectroscopy is one of the few analytical techniques that provide information on the investigated system both from the viewpoint of its structural arrangement and also magnetic order. Here, we demonstrate how 57 Fe Mossbauer spectroscopy can contribute to identification of magnetic phases in rather ordinary Fe-containing materials like natural ochres.
Fe-ochre precipitates were collected at an abandoned antimony deposit in East Slovakia. Three sets of samples were studied: (i) as-collected, (ii) ochres sterilized at 95 degrees C for 30 min, and (iii) Fe-ochre precipitates which were exposed to fungal bioleaching after sterilization.
The Mossbauer spectra from all three batches were recorded at 300, 80, and 5 K. Presence of magnetic phases was revealed only at the lowest temperature.
At higher temperatures, all samples show significant relaxation of magnetic moments which indicates that the crystalline grains are very small and exhibit superparamagnetic behaviour.