The Synthesis of Single-Crystalline BaFe12O19 Nanoparticles by Molten-Salt Method with Surfactant NP-9

Single-crystalline barium ferrite (BaFe₁₂O₁₉) nanoparticles have been successfully synthesized by the molten-salt method. The particles of both samples with and without surfactant NP-9 possess hexagonal plate-like shape. However, BaFe₁₂O₁₉ nanoparticles without NP-9 during the preparation exhibit two different magnetic phases (soft and hard) reflected from the double magnetic hysteresis loops, and the soft magnetic phase was attributed to the defect region in the nanoparticles. Including the surfactant NP-9 in the preparation process, the soft magnetic phase was effectively suppressed, and only the hard magnetic phase was observed, reflected from the single magnetic hysteresis loop. Furthermore, the remanent magnetization and saturate magnetization were increased slightly by using NP-9. These results indicate that NP-9 is an effective additive for the preparation of high-quality single-crystalline ferrite nanoparticles.