Partial cationic inversion-induced magnetic hardening of densely packed 23-nm-sized nanocrystallite-interacting nickel ferrite electrospun nanowires

Although the average crystallite size (23nm) is very close to a critical radius of superparamagnetism, a magnetic hardening (coercive field and saturation magnetization) was observed in interacting single-domain nanogranular nickel ferrite electrospun nanowires as compared with the bulk. The phenomena can be attributed to a small change in the cation occupancy on the spinel sites from (Fe3+)(A)(Ni2+Fe3+)(B)O-4 to F1-delta 3+Ni delta 2+Ni1-delta 2+Fe1-delta 3+](B)O-4 (delta = 3.67%), and an additive interaction of the chain of spheres type. The larger shape anisotropy contribution (K-eff = 8.24 x 10(4) erg/cm(3)) is also as a factor leading to enhanced coercive field. (C) 2013 AIP Publishing LLC.