An investigation of domains and walls in two NdFeB alloys by transmission electron microscopy

Transmission electron microscopy (TEM) is used to investigate the domain structure in NdFeB alloys. The variation of domain period in thinned sections is studied for two different alloys, and an energy minimization model is used to calculate the specific domain wall energy ( sigma ) for each alloy. For the basic alloy (A), a value for sigma of 20.4 mJ/m/sup 2/ is found, while the alloy with additions of Dy (B) has a value which is approximately 10% lower. This result is attributed to a decrease in the Re-TM exchange energy which more than offsets the increase in anisotropy resulting from the addition of Dy. The behavior of domains as they approach a grain boundary is investigated. It is observed that the relative orientation of the c-axes of two adjacent grains is extremely important in determining the behavior of the domain structure at the grain boundary.<
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