Identification of Magnetic Phases in Natural Ochres by Mössbauer Spectroscopy

Z. Gonekováa, M. Miglierinib, c, M. Uríka, M. Bujdoša, M. Cesnekc, T. Kmječd aInstitute of Laboratory Research on Geomaterials, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovakia bSlovak University of Technology in Bratislava, Faculty of Electrical Engineering and Information Technology, Institute of Nuclear and Physical Engineering, Ilkovičova 3, 812 19 Bratislava, Slovakia cDepartment of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, V Holešovičkách 2, 180 00 Prague 8, Czech Republic dDepartment of Low Temperature Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague 8, Czech Republic

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The Mössbauer 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 57Fe Mössbauer 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° for 30 min, and (iii) Fe-ochre precipitates which were exposed to fungal bioleaching after sterilization. The Mössbauer 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.

DOI:10.12693/APhysPolA.137.667 topics: Mössbauer spectroscopy, Fe ochre, fungi, bioleaching