Magnetic properties of the Ni–Cu–Zn system doped with magnesium oxide

• ESR indicated the presence of a single phase.
• The electrical resistivity (ρ) vs. 1000/T shows two regions and one break at Tc.
• The thermoelectric power exhibit a +ve sign indicating the majority carriers are holes.
• The room temperature (Ms) decreases by increasing Mg content.
• This results are useful for the operation of cooling devices..

A series of ferrite samples, Ni0.1Cu0.2MgxZn0.7−x Fe2O4, (x=0.00, 0.15, 0.25, 0.35, 0.45, 0.55 and 0.70) has been prepared by the standard ceramic technique, sintered at 1200 °C for 2 h, and their crystalline structures were investigated by using X-ray diffraction. The IR spectra and the ESR spectra analysis have been studied. DC electrical resistivity, thermoelectric power, charge carriers concentration and charge carrier mobility have been calculated at different temperatures. The value of dc electrical resistivity reach minimum at x=0.35 and above this value the electrical resistivity start to increase. It is noticed that thermoelectric power α for the “Ni–Cu–Zn” system exhibits a positive sign indicating the majority carriers are holes without excluding the presence of electrons. Saturation magnetization Ms for the “Ni–Cu–Zn” system was calculated from M–H loop. It is noted that Ms decreases with Mg content up to x=0.55 and rapidly decrease above x>0.55 for the “Ni–Cu–Zn” system.