ACTA

Spin Relaxation Effects in Oil-Nanomagnetite Ferrofluids - Mössbauer Spectrometry Studies

T. Szumiata^a, M. Gzik-Szumiata^a, K. Brzózka^a, B. Górka^a, M. Gawroński^a, T. Kaczor^a, M. Timko^b, R. Cimbala^c, P. Kopčanský^b, K. Paulovičová^b, M. Rajňák^b
^aDepartment of Physics, Faculty of Mechanical Engineering, University of Technology and Humanities in Radom, E. Stasieckiego 54, 26-600 Radom, Poland
^bInstitute of Experimental Physics SAS, Watsonova 47, 040 01 Košice, Slovakia
^cDepartment of Electrical Power Engineering, Technical University of Košice, Faculty of Electrical Engineering and Informatics, Mäsiarska 74, 041 20 Košice, Slovakia

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Superparamagnetic effects have been studied in oil-nanomagnetite ferrofluid by means of transmission Mössbauer spectrometry. At room temperature it was necessary to slow down Brownian motions of nanoparticle by annealing which make oil more viscous. This procedure is alternative to the freezing in liquid nitrogen. The spectra were fitted with four Gaussian distributions of hyperfine field. Within the analytical model of spin relaxation based on the Liouville super-operators, the mean nanoparticles diameter as well as its standard deviation have been estimated. The reasonable agreement with transmission electron microscopy outcomes has been achieved, especially in the case of the Mössbauer spectra obtained at liquid nitrogen temperature. The additional Mössbauer spectrometry measurements at room temperature in external magnetic fields allowed to verify, if low hyperfine field Mössbauer subspectra originate indeed from the finest particles.

DOI:10.12693/APhysPolA.134.1007
PACS numbers: 75.75.Jn, 31.30.Gs, 75.50.Dd, 75.50.Gg