Ferromagnetic and weak superparamagnetic like behavior of Ni-doped ZnS nanocrystals synthesized by reflux method

In this report we have studied the magnetism induced in the undoped and Ni-doped ZnS nanocrystals synthesized via low temperature reflux method. The average diameter of the undoped and Ni-doped nanoparticles is similar to 3 nm as revealed from transmission electron microscopy and X-ray diffraction (XRD) studies. From XRD studies, the structure of Ni-doped nanocrystals was observed as cubic zinc blende with lattice parameter, a = 0.539 nm. The band gap of the undoped and Ni-doped ZnS nanocrystals, analyzed with UV-visible spectroscopy, was found to be blue shifted as compared to the bulk counterpart. Quenching in photoluminescence spectra was observed at higher Ni concentrations as compared to undoped counterpart. The induced magnetization as analyzed from vibrating samples magnetometer indicated a weak superparamagnetic like behavior in 1 % Ni-doped ZnS nanocrystals, whereas; at 5 and 10 % Ni-doping concentrations, ferromagnetic behavior is indicated.