Structural, magnetic, and optical properties of zinc- and copper-   substituted nickel ferrite nanocrystals
  Ferrite nanocrystals are interesting material due to their rich physical properties. Here we add nonmagnetic dopants Zn and Cu to nickel ferrite nanocrystals, Ni1-xMxFe2O4 (0<=x<=1, M{\in}{Cu, Zn}), and characterize how relevant properties of the samples are modified accordingly. Basically, these dopings cause a rearrangement of Fe+3 ions into the two preexisting octahedral and tetrahedral sites. In fact, this, we show, induces pertinent magnetic properties of the doped samples. In the case of the Cu-doping, the Jahn-Teller effect also emerges, which we identify through the FTIR Spectroscopy of the samples. Moreover, we show an increase in the lattice parameters of the doped samples, as well a superparamagnetic behavior for the doped samples is shown, while the Jahn-Teller effect precludes a similar behavior in the CuFe2O4 nanocrystals. The influences of Zn and Cu substitutions are investigated on the optical properties of nickel ferrite nanocrystals by photoluminescence measurement at room temperature. 
F. Shahbaz Tehrani, V. Daadmehr, A. T. Rezakhani, R. Hosseini   Akbarnejad, S. Gholipour
cond-mat.mtrl-sci