A study of the influence of crystallite size on the electrical and magnetic properties of CuFe2O4

An attempt has been made to clarify the fundamental assumption that the properties of materials change as the crystallite size of the material is reduced below 100 nm. CuFe2O4 samples of different crystallite sizes were prepared by the sol–gel and combustion methods and then analyzed by X-ray diffraction (XRD), thermal analyses (TGA/DTG) and scanning electron microscopy (SEM) techniques. The magnetic properties were studied by measuring the AC magnetic susceptibility (χ) and the Mössbauer spectroscopy. The DC electrical resistivity, dielectric constant, dielectric loss tangent, Curie temperature and hyperfine splitting of the samples change with the crystallite size. The change in the electrical properties is attributed to the formation of discrete energy levels instead of the bands. However, the magnetic parameters change due to the existence of non magnetic surface layers. The isomer shift and the hyperfine splitting show gradual increase with the increase in crystallite sizes.

A plot of crystallite size against the normalized values of resistivity, dielectric constant and the drift mobility of the CuFe2O4 materials.Figure optionsDownload as PowerPoint slideHighlights
► The CuFe2O4 materials of different crystallite sizes of <100 nm are prepared by sol–gel method and others of the size of >100 nm by combustion method.
► The synthesized samples are characterized for different electrical, dielectrical, magnetic and structural properties.
► The results show a sudden change in dc-electrical resistivity, Curie temperature, dielectric parameters, etc. when their crystallite size approaches 84 nm.
► This study shows transition from bulk to the nano regime takes place at the particle size of 84 nm.