STRUCTURE AND PROPERTIES OF COPPER-DOPED NICKEL ZINC FERRITES

The effect of CuO doping on the structure and properties of nickel zin c ferrites close in composition to the commercial grades 400NN2 and 60 0NN was studied by x-ray diffraction, electric and magnetic measuremen ts, microstructural analysis, and nuclear magnetic resonance. The magn etic configurations and charge states of all cations and their distrib ution over the tetrahedral (A) and octahedral (B) sites of the spinel structure were identified. The introduction of CuO gives rise to tetra gonal distortions of the Jahn-Teller active ion Cu2+, residing in the B site. At low-temperatures, these distortions are frozen in and lead, as a result of spin-orbit coupling, to a change in the easy magnetiza tion direction from [111] to [100]. Copper ions are found to affect th e sintering rate and properties of the ferrites studied. The optimum C uO content is determined.