Shenoy, S D; Joy, P A; Anantharaman, M R(Elsevier, February , 2004)
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Abstract:
Nanosized ZnFe2O4 particles containing traces of a-Fe2O3 by intent were produced by low temperature chemical
coprecipitation methods. These particles were subjected to high-energy ball milling. These were then characterised using
X-ray diffraction, magnetisation and dielectric studies. The effect of milling on zinc ferrite particles have been studied
with a view to ascertaining the anomalous behaviour of these materials in the nanoregime. X-ray diffraction and
magnetisation studies carried out show that these particles are associated with strains and it is the surface effects that
contribute to the magnetisation. Hematite percentage, probably due to decomposition of zinc ferrite, increases with
milling. Dielectric behaviour of these particles is due to interfacial polarisation as proposed by Koops. Also the defects
caused by the milling produce traps in the surface layer contributes to dielectric permittivity via spin polarised electron
tunnelling between grains. The ionic mechanism is enhanced in dielectrics with the rise in temperature which results in
the increase of dielectric permittivity with temperature.
Swapna S, Nair; Rajesh, S; Abraham, V S; Anantharaman, M R; Nampoori, V P N(Elsevier, 2006)
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Abstract:
Fine magnetic particles (size≅100 Å) belonging to the series ZnxFe1−xFe2O4 were synthesized by cold co-precipitation methods and their structural properties were evaluated using X-ray diffraction. Magnetization studies have been carried out using vibrating sample magnetometry (VSM) showing near-zero loss loop characteristics. Ferrofluids were then prepared employing these fine magnetic powders using oleic acid as surfactant and kerosene as carrier liquid by modifying the usually reported synthesis technique in order to induce anisotropy and enhance the magneto-optical signals. Liquid thin films of these fluids were prepared and field-induced laser transmission through these films was studied. The transmitted light intensity decreases at the centre with applied magnetic field in a linear fashion when subjected to low magnetic fields and saturate at higher fields. This is in accordance with the saturation in cluster formation. The pattern exhibited by these films in the presence of different magnetic fields was observed with the help of a CCD camera and was recorded photographically.