Anisotropic Sm-(Co,Fe) nanoparticles by surfactant-assisted ball milling

Magnetically hard Sm-2(Co0.8Fe0.2)(17) and SmCo5 nanoparticles have been produced by using surfactant-assisted low- and high-energy ball milling techniques. Surfactants prevent the rewelding of the crashed particles during the milling process. Heptane was used as the milling medium and oleic acid as the surfactant. High-energy ball milling experiments took place in a milling vial with carbon steel balls by using an SPEX 8000M high-energy ball milling machine. The coercivity was found to increase with milling time with values of 2.3 kOe for Sm-2(Co0.8Fe0.2)(17) and 18.6 kOe for SmCo5 after 4 h of milling. Transmission electron microscopy data showed that the milled powders consisted of nanoparticles with an average size of 5-6 nm and a narrow size distribution. Samples deposited on copper coated carbon grid showed self-assembled nanoparticles which could be further aligned when subjected to a magnetic field. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3067851]