Polycrystalline Sn_(1-x)Ni_xO_2 samples were prepared in single-phase form for x=0.02 and 0.07 and were characterized using several experimental techniques. Room-temperature ferromagnetism with transition temperature, Tc, as high as 770 K was observed from the temperature variation of magnetization measurements. Nanoparticles of uniform crystalline phase and composition were identified from the transmission electron microscope images. The initial magnetization curves recorded at 80 and 300 K for both samples could be analyzed based on the bound magnetic polaron (BMP) model, where the size of the BMP is found to increase with temperature. The magnitude of electrical resistivity is found to decrease with doping, and its temperature dependence could be explained based on the variable range hopping mechanism.
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