Correlation between structural, magnetic and electrical properties of nanocrystalline Al3+ substituted zinc ferrite

Nanocrystalline spinel ferrites with general formula ZnFe2−xAlxO4 (0 ≤ x ≤ 2) were synthesized by sol–gel auto-combustion method using tartaric acid as combustion–complexion agent. The relation between structural features, magnetic and electrical properties of these as prepared nano particles was investigated for the first time. Solid phase chemical reactions were monitored by using infrared spectroscopy, indicating finally the absence of organic phases. The XRD analysis shows single phase cubic spinel structure for all compositions studied. The crystallite size estimated by Scherrer formula has been found in the range of 9–24 nm. The cation distribution in all samples have been estimated using a mathematical model and the results show that all compounds have mixed ionic distribution. The magnetic properties of samples were studied by using vibrating samples magnetometer and were showing that the saturation magnetization decreases nonlinearly with the increase in Al3+ content. The electrical analysis showed very low values of dielectric loss at frequencies over 1 MHz. The results obtained for real (ε′), imaginary (ε″) part of the dielectric constant and loss tangent (tan δ) show normal behavior with frequency, which was explained on the basis of interfacial polarization according to Maxwell–Wagner model and Koopʹs phenomenological theory.