Ferrite nanocrystals are an interesting material due to their rich physical properties. Here we add non-magnetic dopant Cu to nickel ferrite nanocrystals, Ni 1−x M x Fe 2 O 4 (x = 0.2, 0.4, and 0.6) M = Cu, and study how relevant properties of the samples are modified accordingly. The grain size and the surface morphology were studied by scanning electron microscopy (SEM).Basically, these doping 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 Cu doping, the Jahn-Teller effect also emerges, which we identify through the Fourier transform infrared 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, while the Jahn-Teller effect precludes a similar behavior in the CuFe 2 O 4 nanocrystals.