Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8152451 | Journal of Magnetism and Magnetic Materials | 2018 | 7 Pages |
Abstract
Structural and magnetic properties of ZnFe2O4 nanograins, prepared by high-energy ball milling and annealed, were systematically studied by X-ray diffraction, 57Fe Mössbauer spectroscopy and AC magnetic susceptibility measurements. Disordered spinel-like structure, with a grain size of 12â¯nm, is established after 200â¯h of milling. While the 300â¯K Mössbauer spectrum of the as-milled sample (200â¯h) displays broad magnetic absorption lines, characteristic of a disordered system, the magnetization data do not show a magnetic phase transition between 4 and 300â¯K. At low temperatures, the Mössbauer spectra suggest the presence of two distinct ferrite magnetic phases: one attributed to the grain core (crystalline-like phase), with magnetic ordering temperature of about 90â¯K, and one showing a magnetic hyperfine field distribution; the latter is associated with a chemically disordered phase (grain boundary contributions). Annealing the 200â¯h sample at 973â¯K leads to an improvement of atomic ordering of the spinel structure (reduction of cationic inversion) and average grain size of about 17â¯nm. AC magnetic susceptibility shows a cusp at about Tâ30K, whilst Mössbauer experiments in the same sample reveal magnetic blocking in the same temperature range. The frequency dependence of susceptibility suggests the formation of a cluster-glass-like state. High temperature susceptibility can be described with a Fulcher law of interacting magnetic clusters.
Related Topics
Physical Sciences and Engineering
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Condensed Matter Physics
Authors
E.F. Procopio, C. Larica, E.P. Muniz, F.J. Litterst, E.C. Passamani,