In this paper, mixed spinel Co-Mn-Cr ferrite with varying chromium content have been investigated to deduce the relation between the structure and some physical properties; electric, optical and magnetic.
Nano-crystalline Co0.7Mn0.3CrxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1) were synthesized via co-precipitation route. The obtained particle size from transmission electron microscope (TEM) micrographs is close to the crystallite size calculated from X-ray diffraction (XRD) by Sherrer's formula, and the particle size distribution is regular. The infrared spectra represent two strong absorption bands around 600 - 400 cm−1, which confirm the presence of M-O stretching bond. The mechanical properties enhanced by adding Cr3+ ions. The optical band-gap calculated from UV-visible spectroscopy is quite affected by adding Cr3+ ions because of particle size reduction. The saturation magnetization (Ms) and the coercivity (Hc) decrease with Cr3+ ions substitution. The variations of the electrical conductivity and drift mobility with temperature were also investigated. The conduction mechanism changed from electron hopping to polaron hopping by raising the temperature. Superparamagnetic Co0.7Mn0.3CrxFe2-xO4 (x ≥ 0.6) nanocrystals can be used in biomedical applications and low power-loss applications. The sample Co0.7Mn0.3Cr0.2Fe1.8O4 has high squareness ratio (Mr/Ms) and, it may be suitable for memory applications.