In this study, the ultra-fine NiCuZn-ferrite was prepared by a coprecipitation method. The magnetic properties were investigated in terms of calcining temperature. The ferrite powders, Ni(0.206)Cu(0.206)Zn(0.618)Fe(1.94)O(4-delta), were initially heat treated at various temperatures of 300-750 C, and then sintered at the final temperature of 900 degrees C. The average particle size calculated by a XRD pattern and confirmed by a transmission electron microscope (TEM) micrograph was 7.5 nm. The calcining temperature was an important factor for microstructures and magnetic properties of the sintered ferrite. Scanning electron microscope (SEM) micrographs showed a uniform grain growth with small pores and high densification at the calcining temperature of 450 degrees C. From the results of magnetic property measurements, the ferrite calcined at 450 degrees C showed higher initial permeability (170) and quality factor (72) than those of other calcining temperatures. (C) 2008 Elsevier Ltd. All rights reserved.