Magnetic and structural properties of zinc-doped nickel ferrite
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, M s, 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-xFe2O 4 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.
Condensed matter physics
Chattrakun, Kanokporn, "Magnetic and structural properties of zinc-doped nickel ferrite" (2011). ETD Collection for University of Texas, El Paso. AAI1494338.