Chemical synthesis and characterization of SmCo₅/Co magnetic nanocomposite particles

Abstract: Magnetic nanocomposite material has been widely focused for the potential to become the next generation of magnetic material. In this paper, two kinds of chemical coating methods were used to prepare SmCo₅/Co nanocomposite particles which were further characterized and compared. The two methods were carried out by using different materials and at different temperatures. In Method I, oleylamine (OAm), oleic acid and Ca(acac)₂ were used and the reaction was carried out at the temperature of 300 °C. In Method II, anhydrous isopropanol, polyvinylpyrrolidone (PVP), N₂H₄·H₂O and CoCl₂·6H₂O were used and the reaction temperature was ~ 55 °C. It was found that by using the two methods, the growth and the crystal structure of the Co nanoparticles (NPs) are different. In Method I, epitaxial growth on the surface of SmCo₅ NPs was observed and the Co NPs were in a face-centered close packing crystal structure. While in Method II, the coated Co NPs were self-nucleated with a crystal structure of hexagonal close packing. Using Method II with the addition of surfactant, anisotropic nanocomposite particles were achieved with an enhanced saturated magnetization of 84.2 A·m²·kg⁻¹. And the coercivity change of the NPs illustrates that a nonmagnetic interlayer between the hard and soft magnetic phase is beneficial to maintain the coercivity. Graphic abstract: [Figure not available: see fulltext.]