Enhanced saturation magnetization and stability of magnetic nanofluids based on FeCo@CoFe2O4 nanoparticles

Abstract

Low saturation magnetization and poor stability caused by agglomeration and sedimentation are two main factors restricting practical applications of magnetic nanofluids (MNFs). Here, we synthesized FeCo@CoFe2O4 core-shell particles using a simple one-step polyol method and prepared of octane-based MNFs with high saturation magnetization and excellent stability. The FeCo@CoFe2O4 particles have regular spherical morphology with homogeneous diameter of about 13 nm. The saturation magnetization of FeCo@CoFe2O4 particles is 102 emu g−1, which is almost twice as much as that of CoFe2O4 particles. Besides, the MNFs with FeCo@CoFe2O4 particles are superparamagnetic and their saturation magnetization is 7.24 emu g−1. FeCo@CoFe2O4 MNFs exhibit stronger magnetic responsiveness than that of CoFe2O4 MNFs, which reaches 5175.74 cP under an external magnetic field of 534 Gs. Moreover, under an external magnetic field of 200 mT, the MNFs with FeCo@CoFe2O4 particles exhibit excellent stability and their magnetic weights decrease by 0.149 g for 289 h, which makes these MNFs have potential to apply in long-term use and magnetoviscous fields.