A rheological phase reaction method was developed to synthesize the nanocrystalline lanthanum-substituted lithium–nickel ferrites, Li 0.25Ni 0.5La x Fe 2.25− x O 4 ( x=0.00, 0.025, 0.05, 0.075, 0.10). The structure, morphology, and magnetic properties of the as-prepared Li 0.25Ni 0.5La x Fe 2.25− x O 4 ferrites were characterized by powder X-ray diffractometer (XRD), scanning electron microscope (SEM), and vibrating sample magnetometer (VSM). It was shown that Li 0.25Ni 0.5La x Fe 2.25− x O 4 ferrites exhibited the single-phase spinel structure. The lattice parameters increased with increasing the La content, whereas the crystallite sizes decreased. The magnetic properties of Li 0.25Ni 0.5La x Fe 2.25− x O 4 ferrites were strongly affected by the La content. The saturation magnetization decreased, while coercivity increased with increasing the La content.