Effect of Cu²⁺ substitution on structural and magnetic properties of Ni–Zn ferrite nanopowders

In this study copper substituted nickel–zinc ferrite powders with the general composition Ni_0.6−xCu_xZn_0.4Fe₂O₄ (x = 0, 0.05, 0.1, 0.15, 0.2, and 0.25) were prepared via auto-combustion sol–gel method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy, Mössbauer spectroscopy, vibrating sample magnetometer (VSM) and superconducting quantum interference device analysis were carried out in order to characterize the structural and magnetic properties of particles. The XRD results confirmed the formation of single phase spinel ferrite particles for all of the samples. The results of FTIR analysis indicated that the there are two main frequency bands, namely, the high frequency band observed at ~577 cm⁻¹ and the low frequency band observed at ~450 cm⁻¹. These two bands correspond to the intrinsic vibrations of tetrahedral and octahedral Fe³⁺–O²⁻ complexes, respectively, and are the characteristics of all the ferrite materials. The size of particles was around 80–800 nm. The VSM results revealed that with an increase in the amount of copper in ferrites, the saturation magnetization increased. Saturation magnetization increased to 97 emu/g for x = 0.05 at room temperature and increased to 261 emu/g for x = 0 and 0.05 at 2 K. The results indicated that the powder is suitable for the application in multilayer chip inductor due to its low temperature sinterability and good magnetic properties.