Understanding magnetic interactions in SrFe 12 O 19 /CoFe 2 O 4 nanocomposites: role of particle structure on exchange spring magnet behaviour

This study explores the impact of particle structure on the magnetic properties of SrFe 12 O 19 /CoFe 2 O 4 nanocomposites. The investigation focuses on variations in particle sizes of SrFe 12 O 19 (SHF) and CoFe 2 O 4 (COF) with a mass ratio of 80:20, considering micro-scale poly-crystallite particles (Pp) and nano-scale mono-crystallite particles (Mp). Four sample structures (COM 1 , COM 2 , COM 3 , COM 4 ) were prepared, each with different combinations of poly-crystallite and mono-crystallite particles. Morphological analysis through scanning electron microscopy and energy-dispersive x-ray spectroscopy revealed consistent grain shape and size post-sintering. Magnetic properties analysis using Permagraph indicated that grain fineness and uniformity influence the resulting magnetic properties, with composite samples featuring nano-sized hard or soft phases showing improved M r , M s , and (BH) max values compared to individual phases. The nanocomposite sample COM 4 , characterized by fine and uniform particle size, exhibited the highest remanence magnetization, M r (34.55 emu g −1 ), saturation magnetization, M s (66.44 emu g −1 ), and the maximum energy product, (BH) max (1.17 MGOe).