Partitioning of Ga and Co atoms in a Fe3B/Nd2Fe14B nanocomposite magnet

Partitioning of Co and Ga atoms in nanocrystalline Nd4.5Fe73B18.5Co3Ga1 at various stages of crystallization has been studied by atom probe field ion microscopy. In the early stage of crystallization, Co and Ga atoms are rejected from primary particles of the soft magnetic Fe3B phase and partitioned to the amorphous matrix phase. These atoms are enriched at the Fe3B/amorphous interfaces in this stage. Three crystalline phases (Fe3B, Nd2Fe23B3, and Nd2Fe14B) are present in the fully crystallized state, and Ga partitions preferentially only to the Nd2Fe14B phase. In a fully crystallized Fe3B/Nd2Fe14B nanocomposite with optimum magnetic hardness, Co and Ga atoms are partitioned to the Nd2Fe14B phase, and evidence for a slight enrichment of Ga atoms at the Nd2Fe14B/Fe3B interface has been found. Based on these results, the role of Ga and Co additions for improved;hard magnetic properties is discussed. (C) 1998 American Institute of Physics. [S0021-8979(98)08412-6].