Formation and magnetic properties of nanosized Sm2Co17 magnetic particles via mechanochemical/thermal processing

Nano-sized Sm2Co17 magnetic particles have been prepared by mechanical milling and subsequent heat treatment of a mixture of Sm2O3, CoO and Ca with a suitable amount of CaO as diluent. The mechanical milling produced a nanostructured composite consisting of a nanocrystalline CaO supersaturated with Ca, CoO and Sm2O3, Co nanoparticles and a small amount of CoO. Heat treatment of as-milled powders at temperatures above 300 degrees C resulted in the formation of ultrafine Sm2Co17 particles of 10-250 nm in size embedded in a CaO matrix. The particle size of Sm2Co17 grew larger and its distribution became wider with increasing heat treatment temperature. A high coercivity of 14.2 kOe was measured on the ultrafine Sm2Co17 particles embedded in the CaO matrix in the sample heat treated at 800 degrees C. (C) 1999 Acta Metallurgica Inc.