Temperature and composition dependence of magnetic properties of cobalt–chromium co-substituted magnesium ferrite nanomaterials

The temperature and composition dependence of magnetic properties of Co–Cr co-substituted magnesium ferrite, Mg1−xCoxCrxFe2−xO4 (x=0.0–0.5), prepared by novel polyethylene glycol assisted microemulsion method, are studied. The synthesized materials are characterized by the Mössbauer spectrometer and standard magnetic measurements. Major hysteresis loops are measured up to the magnetic field of 50 kOe at 300, 200 and 100 K. The high field regimes of these loops are modeled using the Law of Approach to saturation to determine the first-order cubic anisotropy coefficient and saturation magnetization. Both the saturation magnetization and the anisotropy coefficient are observed to increase with the decrease in temperature for all Co–Cr co-substitution levels. Also, both the saturation magnetization and the anisotropy coefficient achieved maximum value at x=0.3 and x=0.2, respectively. Explanation of the observed behavior is proposed in terms of the site occupancy of the co-substituent, Co2+ and Cr3+ in the cubic spinel lattice. - Highlights: ► Mg1−xCoxCrxFe2−xO4 are synthesized by novel PEG assisted microemulsion method. ► Co–Cr occupied octahedral site confirmed by the Mössbauer analysis. ► High field regime of M–H loops are modeled using the Law of Approach to saturation. ► The values of MS, Mr, HC and K1 are found to increase with decreasing temperature.