82nd Magnetic Materials Center Seminar
July 30, 2008, 9:00-
7th floor small seminar room, Sengen

H. S. Goripati


Microstructure and coercivity evolution during desorption and recombination of HDDR NdFeB magnets
W. Li
The hydrogenation disproportionation desorption recombination (HDDR) process is widely used to get fine grain sized NdFeB powders. It consists of a sequence of stages. In this work, our investigation shows that in the desorption and recombination stage the hold time between 15 and 20 is critical for the microstructure and also the magnetic performance evolution of Nd12.5Fe73Co8B6.5 magnet. By increasing hold time of DR process, the coercivity can be increased sharply from 100 kA/m to nearly 1000 kA/m. The appearance of the Nd enriched layer is the reason for the coercivity enhancement. This thin layer can pinning the domain wall motion effectively and thus increase the coercivity,which can be confirmed by lorenz observation.

Atomic site disordering in Co2Fe(Al,Si) and asymmetric double tunnel junctions
K. Inomata
Two topics are presented. The first is the analysis of atomic site disordering in bulk and thin film Co2FeAlxSi1-x Heusler alloys using 59Co NMR. The disordering is shown to be the swapping between Al and Fe atoms, while Co and Si atoms almost occupy the regular sites. The second one is the introduction of asymmetric double tunnel junctions, which can provide unique and fantastic characteristics in transport properties.