Grain boundary oxide layers in NdFeB-based permanent magnets

The microstructure of grain boundaries (GBs) in the commercial NdFeB-based alloy for permanent magnets has been studied. It is generally accepted that unique hard magnetic properties such alloys are controlled by thin layers a Nd-rich phase Nd2Fe14B/Nd2Fe14B GBs. These GB ensure isolation Nd2Fe14B grains from each other. usually supposed contain metallic Nd or intermetallic compounds. However, frequently tangible amount neodymium oxide Nd2O3 at triple junctions between grains. goal this work was to check whether GBs could also phase. Indeed, screening with EELS-based elemental analysis permitted observe some these not only neodymium, but oxygen. More detailed high-resolution transmission electron microscopy (HR TEM) showed crystalline and have lattice Nd2O3. In turn, Lorentz micro-magnetic contrast TEM Nd-oxide prevent migration domain walls one another during remagnetization. This finding proves layers, similar those compounds, can needed high coercivity. Therefore, be used further development magnets.