Date of Award

2011-01-01

Degree Name

Master of Science

Department

Physics

Advisor(s)

Cristian Botez

Abstract

We have used dc-magnetization, ac-magnetic susceptibility and x-ray diffraction (XRD) to investigate the microscopic origin of the magnetic property modifications induced by zinc doping in bulk and nano-sized nickel ferrite. Magnetic measurements indicate that the nanoparticle energy barrier to magnetization reversal, EB, and the bulk saturation magnetization, Ms, follow similar dependences on the zinc doping fraction, x. Both these magnetic quantities initially increase with increasing x, reach a maximum at x~0.5, and eventually decrease upon further doping. Synchrotron and laboratory powder XRD data show no evidence of significant structural modifications for x~0.5: we find the lattice parameter of ZnxNi1-xFe2O4 to exhibit a linear increase with x, and the inverse spinel crystal structure of NiFe2O4 (x=0) to persist throughout the entire zinc doping range 0≤x≤1. Instead, A- and B- site occupancy refinements via Rietveld analysis reveal an indirect mechanism by which Ni2+ ions, which reside in B (octahedral) sites, are replaced by Zn2+. In this scenario, zinc is incorporated into A (tetrahedral) sites where it displaces Fe3+ ions, which migrate to the B sub-lattice and replace Ni2+. This doping mechanism is consistent with the observed magnetic property enhancement at x~0.5.

Language

en

Provenance

Received from ProQuest

File Size

54 pages

File Format

application/pdf

Rights Holder

Kanokporn Chattrakun

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