2015/10/07 by Gregor A. Zickler, Peter Toson, Zickler, Gregor A. +5
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Magnetic Properties and Applications #Magnetic Properties of Alloys #Magnetic properties of thin films #Materials Science (cond-mat.mtrl-sci)
paper · pdf · doi:10.48550/arxiv.1510.01958
openalex publication_date 2015/10/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We have analysed the influence of the microstructural features, such as\nintergranular grain boundary (GB) phases and misalignment of the hard magnetic\ngrains, on the optimization of magnetization reversal processes in order to\nimprove the coercive field of Nd-Fe-B magnets. The microstructural model of the\ngrains and intergranular phases, which is used for theoretical simulations, has\nbeen derived from a detailed nanoanalytical TEM/STEM study of a Dy/Tb free\nmagnet and a high coercive (Nd,Tb)-Fe-B magnet. Special attention is laid on\nthe EELS analysis of GB with a thickness ranging from 2 - 30 nm. This analysis\nidentified the majority of the GB phases to have about 50 -70 at.% of iron and\nonly a few GBs, which are connecting two nearby grain boundary junctions (GBj),\npossess a similar chemical composition as the adjacent GBj with a low iron\ncontent (< 10 at. %) and a high rare earth and oxygen content. Finite element\nmicromagnetic simulations have been carried out in order to study the influence\nof internal demagnetizing fields determined by the microstructure on the\nmagnetization switching behaviour. Special emphasis was put on the influence of\nthe GB and their magnetic properties, due to their substantial influence on the\nnucleation of reverse magnetic domains and the pinning of domain walls. The\nstrongest reduction of the coercive field is caused by GB with soft\nferromagnetic properties. Shielding the Nd-Fe-B grains from the nucleation\nsites at the GBj with Dy or Tb shells, leads to an increase of the coercivity\nfrom 2.5 to 3.6 T and 2.5 to 4.3 T, respectively.\n