Exploring the effect of exchange coupling in (SrFe9.8Al2La0.2O19)1-x/(Co0.7Zn0.3Fe2O4)x nanocomposites synthesised by sol–gel auto combustion method

• Nanocomposites were synthesised by using the sol-gel auto -combustion technique with the varying weight %. • The crystallite size of hard phase decreased with the increase in weight percentage of soft phase. • X-ray Photoelectron Spectroscopy (XPS) technique probed the electron state of atoms at octahedral and tetrahedral sites. • The inclusion of soft phase into hard phase enhanced the magnetization from 18 emu/g to 48 emu/g. • The nanocomposite ratio x = 0.1 exhibits a high magnetocrystalline anisotropy of 218322 J/m 3 and energy product of 5.5 kJ/m 3 . Extensive research has been conducted over the last decade to develop permanent magnets utilizing less rare earth materials. Exchange-coupled nanocomposite magnets are a fascinating development in the field of permanent magnets. They involve the combination of hard and soft ferrites, resulting in a unique and evolving magnet. Here we present an in-depth structural, morphological and magnetic characterization of ferrite-based nanostructures obtained through a bottom-up sol−gel approach. The combination of high coercivity of a hard phase SrFe 9.8 Al 2 La 0.2 O 19 (SFALO) and high saturation magnetization of a soft phase, Co 0.7 Zn 0.3 Fe 2 O 4 (CZFO), allowed us to develop exchange-coupled bi-magnetic nanocomposites by varying the mass percentage (x = 0, 0.1, 0.2, 0.3, 0.4, 1). Thermogravimetric analysis (TGA) up to 1200 °C was used to investigate the material’s thermal properties with the phase formation temperature. Detailed atomic/nano-scale structural characterizations of these nanocomposites were performed by X-ray diffraction and Transmission Electron Microscopy. The average particle size was calculated from the SEM analysis and it was observed that most of the composites with ratio x = 0.1, 0.3 & 0.4 was 145 nm and x = 0.2 was 165 nm. The Switching Field Distribution (SFD) curve revealed the exchange coupling between soft and hard magnetic particles. The findings indicate that the inclusion of a soft magnetic phase has a considerable impact on the exchange coupling between the hard and soft ferrite phases. As the spinel concentration increased, in the composite the saturation magnetization increased from 18 emu/g to 48 emu/g. From the stroner-wholfrath model, the decrease in the remanence ratio below 0.5 concludes the crystallites are randomly oriented. The nanocomposite with the ratio x = 0.1 was observed with the high magneto crystalline anisotropy of 2183.23 × 10 2 (J/m 3 ) and a high energy product (BH) max of 5.5 kJ/m 3 . The aforementioned features of nanocomposites demonstrate their potential for use in permanent magnet applications.