Magnetic properties and thermal stability of SrFe12O19/γ-Fe4N composites with effective magnetic exchange coupling

The SrFe12O19/gamma-Fe4N composites were fabricated through physical mixing and the mass of gamma-Fe4N nanoparticles was controlled as 0, 5 wt%, 10 wt% and 15 wt% in four batches of experiments. The magnetic properties of the composites were investigated. It was found that when gamma-Fe4N nanoparticles were 5 wt%, and 10 wt%, effective exchange coupling between gamma-Fe4N and SrFe12O19 was observed, and the maximum energy product was increased by 13.5%, and 21.2%, respectively, over pure SrFe12O19. The existence of magnetic exchange coupling between SrFe12O19 and gamma-Fe4N was confirmed by both the shape of their hysteresis loops and Henkel plots. The thermal stability investigation indicated that the thermal treatment could slightly deteriorate the magnetic exchange coupling due to the sintering of gamma-Fe4N nanoparticles, but the maximum energy product was lithe impacted.