Magnetic Hardening Studies and Novel Techniques for Preparation of High Performance Magnets
Final rept. 1 Jan 1990-25 Jan 1992
DELAWARE UNIV NEWARK DEPT OF PHYSICS AND ASTRONOMY
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Our efforts in permanent magnets have been focused on the search for new phases and alloys with high magnetization, large anisotropy, and high Curie temperature that can be used for permanent magnet development and on the magnetic hardening behavior of R-FE-B magnets. The systems studied include Fe- Mo, Co-Zr-B and as-cast NdPr-rich alloys with coercivities exceeding 6 kOe obtained in the latter two samples. Small additions of AI and Cu have been found to increase the coercivity of melt-spun R-FE-B magnets substantially by as much as 8 kOe. The microstructure of the substituted samples is more homogenous with the secondary Nd-AICu-rich phases uniformly distributed throughout the sample. In addition, disturbed lattice regions were observed at most of the grain boundaries. In Cu-substituted melt-spun samples several faults have been observed inside the 2141 grains. This is the first time that defects were observed in a 2141 matrix and they have been attributed to the small solubility of Cu on Fe. As-cast NdPr-Fe1-xMnx-B samples have been found to have large coercivities at cryogenic temperatures. The large coercivities observed are due to domain wall pinning at atomic-size defects caused by the random Mn site occupation leading to sites with fluctuations in exchange and anisotropy because of the extremely thin domain walls.
- Electricity and Magnetism