Magnetic properties of hard-soft SrFe10Al2O19/Co0.8Ni0.2Fe2O4 ferrite synthesized by one-pot sol–gel auto-combustion

• Sol–gel autocombustion method was used to prepare hard/soft magnetic nanocomposite.
• Structural and microscopic analysis confirmed formation of two distinct phases.
• The samples prepared by physical mixing method show a “bee waist” hysteresis loop.
• High level of homogenous mixing of two phases results in single hysteresis loop.
• The relatively strong exchange coupling behavior was observed in nanocomposites.

SrFe10Al2O19/Co0.8Ni0.2Fe2O4 hard/soft nanocomposite ferrites with different content of soft phase have been prepared by simple one-pot sol–gel auto-combustion route. X-ray diffraction (XRD), field emission scanning electron microscopy and vibrating ample magnetometer were employed to analysis of structural and magnetic features of synthesized samples. XRD patterns reflect the formation of hard/soft composites of ferrites without the existence of any kind of secondary phases. Narrow size distributions of particles were formed by sol–gel method. Single smooth hysteresis loops of nanocomposites show the presence of exchange coupling between hard and soft phases. Nanocomposite with 15 wt% of soft phase reaches the highest Mr/Ms ratio of 0.63. Compared to the physical mixing of hard/ soft nanocomposites, the one-pot sol–gel auto-combustion method could be considered as a suitable method for synthesizing exchange coupled magnet.