Nanocrystallite size effect on σs and Hc in nanoparticle assemblies

This article presents how Ni0.35Zn0.65Fe2O4 Mixed ferrite nanocrystallites are obtained at low temperatures (500degreesC) by a new chemical method of synthesis, as well as the effect of the nanocrystallites' size on the magnetic properties. We have shown by means of X-ray diffraction that the resulting ferrite is made up of nanocrystallites and the average size of these nanocrystallites-calculated with the Scherer formula-depends on the annealing temperature. When the temperature is modified from 500degreesC to 900degreesC, the nanocrystallites' average diameter ranges from 20.3 to 37.9 nm. The magnetic properties of the nanocrystallite assembly are discussed for values around the single-domain and the multidomain state that results both experimentally and from theoretical calculations. The nanocrystallites are single-domain up to an average diameter of similar to29 nm, whereas above this value they have an incipient structure of Weiss domains. (C) 2002 Elsevier Science B.V. All rights reserved.