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Ferrite nanocrystals are an interesting material due to their rich physical properties. Here we add non-magnetic dopants Zn and Cu to nickel ferrite nanocrystals, Ni_1−x M _x Fe₂O₄ (0≤x≤1, M=Cu, Zn), and study 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 Fourier Transform Infra-Red 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 …