Structural, magnetic and dielectric properties in Cu substituted Ni-Zn ferrite for sensors applications

Copper substituted NiZn ferrite powder of a chemical formula Ni 0.5−x Cu x Zn 0.5 Fe 2 O 4 (0≤ × ≤0.3) is synthesized by auto combustion process at 350°C followed by the calcination at 600, 900 and 1000°C for 2h. The derived powder shows well distinct total seven peaks of cubic spinel structure with space group Fdℨm. The considerable increments in the lattice constant and the reduction in an average crystallite sizes are observed with increasing the Cu content. At the optimal condition of x = 0.1, the crystallite size as small as 26 nm and the coercivity as high as 158 Oe is obtained in samples calcined at 600°C. The dielectric (έ, e″, and tanδ) analyses show the frequency sensitive behavior in the low frequency region and the frequency independent characteristics at high frequency side due to the Maxwell-Wagner type of interfacial polarization and also due to hopping of charges between Fe2+ ↔Fe3+. The highest dielectric constant ∼ 48 at 1 kHz and the lowest dielectric loss ∼ 0.06 at 4 MHz are obtained in the studied frequency range, whereas the maximum frequency sensing response ∼ 92% is observed at 4 MHz in same sample.