Relations of the structure and thermal stability of NdFeB magnet with the magnetic alignment

Relationships between the alignment magnetic field H-align of NdFeB powders and the thermal stability of their sintered magnets were investigated on the base of observing the domain structure and microstructure. The thermal stability increased before 0.6 T and then decreased with the enhancement of H-align. The action of H-align is manifested in rotating magnetic particles and higher H-align increases the alignment degree of matrix phase and optimizes the magnet microstructure, thus increasing the magnetic ordering and minimizing the magnetostatic energy of aligned particles. Better magnetic ordering and lower magnetostatic energy are sensitive to the temperature, accounting for the reduction of thermal properties after 0.6 T.