**Abstract**

The present chapter summarizes the synthesis and characterization of Zinc Copper (ZnCu) ferrites due to their wide range of applications in many areas. ZnCu ferrites are soft magnetic materials that have exceptional electrical, magnetic, and optical properties. ZnCu ferrites possess high resistivity, permeability, permittivity, saturation magnetization and low power losses, and coercivity. The above features of ZnCu ferrites find application in designing transformers, transducers, and inductors. Ferrites are also used in magnetic fluids, sensors, and biosensors. Apart from these advantages, they play a vital role in practical appliances like mobile, laptops, mobile chargers, refrigerators, washing machines, microwave ovens, printers, and so on. Therefore, the present focus is on the literature of techniques of the synthesis, their characterization, the effect of doping on the behavior of ZnCu ferrite, and, finally, their potential application in technology.

**Keywords:** spinel, ferrites, magnetic, surface morphology, synthesis techniques

## **1. Introduction**

A ferrite is a ceramic material that is made up of iron oxide(Fe2O4) in massive proportion mixed with a metallic element such as barium (Ba), manganese (Mn), nickel (Ni), zinc (Zn) in small proportions [1–9]. The nature of iron oxide and the metal is electrically non-conducting and ferrimagnetic. Ferrimagnetic materials possess unequal opposing magnetic moments which help to retain spontaneous magnetization. Ferrites are generally classified into two types: hard ferrites [10, 11] and soft ferrites [12–15]. Hard ferrites have a high coercivity to magnetize. These materials are used in making permanent magnets which find application in the loudspeaker, washing machine, communication systems, switch-mode power supplies, dc-dc converters, microwave absorbing systems, and high-frequency applications [16–23]. On contrary, soft ferrites have low coercivity as a result of which their magnetization can easily be altered. Soft ferries are good conductors of the magnetic field which paved the way in developing transformer cores, high-frequency inductors, and microwave components [24–38]. Further, soft ferrites include high resistivity, low cost, temperature stability, low loss, and high permeability [39–42]. The most significant soft ferrites are ZnCu ferrites with high permeability and saturation magnetization [43–49]. Properties of these nanomaterials can be modified by substitution of diamagnetic or

paramagnetic cations and their distribution in the spinel structure which alters the grain sizes, distribution, and surface morphology. The attribution of ZnCu ferrites is dependent on the synthesis methods and concentration of doping [50]. Cu-Zn spinel ferrites possess excellent magnetic behavior that depends on the concentration of Zn2+ ions in CuFe2O4. The large saturation magnetization (Ms), high initial permeability, and high resistivity of Cu-Zn ferrites make them a prominent material in electrical switches, memory devices, inductors, and antenna cores [51, 52]. Cu2+ has one unpaired electron, and Zn2+ has no unpaired electron. So, the replacement of Cu2+ ion by Zn2+ ion enhances the strength of magnetic ions participating in the exchange interaction. Moreover, the substitution of Zn2+ in place of Cu2 + changes the cation distribution and arrangement in the spinel structure. So, it is interesting to study the effect of Zn2+ substitution on the magnetic properties of Cu-ferrite nanoparticles. Moreover, Zn2+ substitution with higher concentration stabilizes the cubic phase of Cu-ferrite. The importance of Zn-Cu ferrites based on a comprehensive review is summarized.
