Size dependent structural and magnetic properties of Al substituted Co–Mg ferrites synthesized by the sol–gel auto-combustion method

• Well-crystalline Co0.7Mg0.3AlFeO4 nanoparticles with small grain size were obtained.
• The approach is sol–gel auto-combustion technique for obtained nanoparticles.
• The prepared Co0.7Mg0.3AlFeO4 ferrites are decent soft materials with low coercivity.
• The minor decrease in lattice parameter with increase of temperature was observed.

Single phased nanocrystalline Co0.7Mg0.3FeAlO4 ferrites having low coercivity were synthesized by the sol–gel auto-combustion route. The subsequent powder materials were sintered in a temperature range of 800–1200 °C for 2 h. The effects of sintering temperatures on the structure, morphology and magnetic properties of the prepared soft magnetic material were studied. X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and magnetic property measurement system (MPMS) were used to characterize the samples. X-ray diffraction analysis confirmed a single-phase cubic spinel structure and ruled out the presence of impurities like hematite. The higher sintering temperatures have caused in enhanced mark of crystallinity and bigger average grain size of the nanocrystals. A slight decrease in lattice parameters was noticed with a rise of grain size. Magnetic measurements revealed that grain size increase led to a decrease in the coercivity and, in difference, an increase in the saturation magnetization.

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