Surfactant Removal Study for Nano-Scale ${\rm SmCo}_{5}$ Powder Prepared by High Energy Ball Milling

In the present study, nano-flake SmCo₅ powders with typical flake thickness of 300 nm were prepared by high energy ball milling using valeric acid as a surfactant. In order to remove the surfactant the as-milled powders were heat treated in argon and the effect of the annealing temperature on structural and magnetic properties of the resulting powder was investigated. Partial (58%) and nearly complete (96%) surfactant removal was observed by DSC after treatments at 200°C and 400°C, respectively, without oxide formation detectable by powder X-ray diffraction. Demagnetization measurements revealed suppression of the energy product (BH)_max and dramatic decrease in coercivity (H_ei) after annealing. The results indicate that even a modest heat treatment of SmCo₅ nano-powder severely degrades its magnetic properties. Either alternative methods of surfactant removal must be considered, or the surfactant must remain during further powder processing.