Magnetic and Mössbauer Studies on Nanostructured CoCrxFe2-xO4 (0 = x = 1) Spinel Ferrites Prepared by Sol-Gel Auto-Combustion Method.

Low temperature preparation of nanostructured CoCrxFe2-xO4 (0

Investigations of Magnetic Properties of Oleic Acid and Oleyl Amine Capped Nanostructured Co( x) Ni(1−x) (0.2 ≤ x ≤ 0.8) Alloys.

In this study, nanocrystalline oleic acid and oleyl amine capped Co x Ni1−x alloys (x = 0.2, 0.4, 0.6, 0.8) have been synthesized via chemical reduction route. As-prepared as well as annealed samples were characterized using FTIR spectroscopy, X-ray diffraction and transmission electron microscopy. CoNi alloys were found to be capped with oleic acid-oleylamine complex even after heat treatment up to 400 °BC. XRD patterns confirm that the CoNi alloys crystallize in pure fcc phase with average crystallite sizes in the range of 8­11 nm. TEM micrographs confirm nearly spherical morphologies with narrow particle size distribution of the synthesized CoNi alloys. Average TEM particle sizes range from 7 nm to 12 nm. As-prepared as well as annealed CoNi alloys are ferromagnetic in nature at 298 K. M s values for annealed CoNi alloys are found to be in the range of 25­59.6 emu/g after correction for weight fraction of capped matrix and H c values are in the range of 52­314 Oe. Observed magnetic properties have been interpreted on the basis of size effects, altered crystal anisotropies and spin canting on the surface. FC/ZFC magnetization measurements show magnetic irreversibility and superparamagnetic blocking of nanoparticles due to strong dipolar interactions and particle size distribution. A structure-property correlation in CoNi alloys has been attempted in this investigation.