Exchange spring magnetic behavior of Sr0.3Ba0.4Pb0.3Fe12O19/(CuFe2O4)x nanocomposites fabricated by a one-pot citrate sol-gel combustion method

In this study, hard/soft Sr0.3Ba0.4Pb0.3Fe12O19/(CuFe2O4)x nanocomposites with various contents of the soft phase (x = 1, 2, 3, 4, and 5) have been synthesized via a one-pot citrate sol-gel route. The structure and magnetic properties of the prepared specimens were investigated using X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM) techniques as well as a vibrating sample magnetometer. The obtained XRD patterns revealed the formation of hard/soft ferrite nano-composites without secondary phases. The magnetic results showed that all the prepared nanocomposite magnets exhibit a good single-phase magnetic behavior, proving that the magnetic hard and soft phases are well exchange coupled. The dipolar interactions in the produced magnets were dominated by the exchange-coupling interactions at lower contents of the soft phase. Furthermore, the optimal values of saturation and remanent magnetizations, coercivity, and squareness ratio were obtained for the Sr0.3Ba0.4Pb0.3Fe12O19/CuFe2O4 nanocomposite magnet due to the dominance of exchange-coupling interaction. The greatest value of the maximum energy product, which represented the ultimate figure-of-merit for permanent magnets, was observed for the Sr0.3Ba0.4Pb0.3Fe12O19/CuFe2O4 composite, suggesting its potential applications in magnet fabrication and highly sensitive magnetic recording media.