Structural and magnetic properties of nanocrystalline yttrium substituted cobalt ferrite synthesized by the citrate precursor technique.

CoFe 2− x Y x O 4 ( x = 0.0 and 0.05) compound has been synthesized by citrate precursor method and, their structural and magnetic properties have been investigated. X-ray diffraction and Raman spectroscopy have been used to confirm the formation of single phase cubic spinel structure. The X-ray diffraction patterns have been analyzed employing Rietveld refinement technique. The surface morphology and particle size of the samples have been examined using FE-SEM and TEM. Substituting small amount of Y 3+ cation causes significant reduction of the particle size. The magnetic hysteresis curve recorded at room temperature using VSM over a field range of ±2 T shows enhancement in coercivity and reduction in highest magnetization with the Y 3+ substitution. The enhancement of coercivity is attributed to the transition from multidomain to single domain state. The cubic magnetocrystalline anisotropy constants for present samples has been determined by “law of approach” to saturation which suggests the smaller value for substituted sample ( x = 0.05) than that of unsubstituted sample ( x = 0.0). ZFC and FC magnetization measurement over the temperature range 300–900 K shows blocking temperature is far above than room temperature. The decrease of highest magnetization and magnetocrystalline anisotropy constant is ascribed to weakening of superexchange interaction and surface effect. [ABSTRACT FROM AUTHOR]