The rod-shaped Ni_0.5Zn_0.5Fe₂O₄ particles were synthesized via a topotactic reaction, in which goethite (α-FeOOH) particles are the main constituents. The phases, microstructures and magnetic properties of these particles were studied using XRD, FE-SEM and VSM. The precursor solution consisted of NiSO₄·xH₂O, ZnSO₄·xH₂O, goethite and D.I. water werereacted at four different temperatures (50, 70, 90, 100℃) to generate four differently precipitated particles respectively. During the co-precipitation reaction, the pH of the solution was maintained at 8.0 using NaOH. The particles coprecipitated and calcined at a temperature of 700℃, exhibited a rod-shape similar to its original goethite, which means that the shape of Ni-Zn ferrite particles can be topotactically controlled by the goethite. The particles synthesized at 70 and 90℃ have a saturation magnetization of 29 and 35 emu/g respectively; representing better values than the ones synthesized at the 50 and 100℃, in which some second phases such as Fe₂O₃ were observed.