Preparation, microstructure and magnetic properties of Sm(Co,Hf)7/Co nanocomposite particles by polyol method

Hard/soft Sm-Co/Co nanocomposite particles were prepared by reducing CoCl2·6H2O in the solution containing ball-milled Sm(Co, Hf)7 particles by a simple polyol method with ethylene glycol as the solvent. Phase composition, microstructure and magnetic properties of the particles were analyzed by XRD, TEM (HRTEM) and VSM, respectively. It has been found that Sm-Co/Co core/shell structure is formed in which the Co shell is 3-5 nm in thickness and mainly exists in hcp-Co phase. At the same time, fcc-Co tends to nucleate and grow independently between Sm-Co particles. The formation mechanism of Sm-Co/Co composite particles is discussed and corresponding model is established. Sm-Co/Co composite particles perform obvious remanence enhancement effects especially after being heated at 450 °C for 15 min