2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Optimization of Magnetic Properties in Cobalt Ferrite Nanocrystals

Y. CedeƱo, O. Perales-Perez, F. Roman, R. Singhal and M.S. Tomar
University of Puerto Rico, Mayaguez Campus, PR

Keywords:
ferromagnetic, cobalt ferrite, nanocrystals

Abstract:
Among the various ferrite materials for magnetic recording applications, cobalt ferrite (CoFe2O4) possesses excellent chemical stability and good mechanical hardness. Furthermore, the large positive first order crystalline anisotropy constant has made this ferrite a promising candidate for magneto-optical recording. The success of its practical application will depend on the capability of controlling composition, structure and particle size at the nanoscale. Our research involves a modified co-precipitation approach that allows controlled growth of cobalt ferrite nanocrystals within the superparamagnetic and single domains limits and, subsequently, high coercivity at room-temperature. This size-controlled synthesis approach became possible by controlling the oversaturation conditions during ferrite formation. XRD and FT-IR analyses confirmed the formation of the ferrite for a reaction time as short as five minutes. HRTEM analysis confirmed the growth of ferrite nanocrystals by prolonging the reaction time. Room-temperature M-H measurements verified the influence of synthesis conditions and crystal size on the magnetic properties of ferrite nanocrystals. The coercivity was increased under controlled flow-rate conditions; it increased from 460 Oe, (no control on flow rate), up to 1337 Oe for 10 ml/min. A complete discussion of the optimization of the magnetic properties in ferrite nanocrystals will be de presented.

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