Magnetic properties of macro-core-shell heat-dendritic Nd-Fe-B magnets prepared by Dy-Cu diffusion and their microstructure near the center and center (B); Multi-layer schematic diagram of the delaminated (A, b, c, d), a low coercivity magnet (e, f, g, h) and a high coercivity magnet The evolution of the domain structure during the anti-magnetization process (D) shows that the coercive layer produces stronger 'pinning' due to the magnetic coupling of the high coercivity layer in the composite multi-layer structure Obtain a strong anti-demagnetization capability
In the field of rare earth permanent magnetic materials, it is relatively mature to research and develop the magnetic magnetic material with macroscopic magnetic homogeneity by using the coupling mechanism of the magnetic phase on the microscopic scale such as nanometer or submicron. However, for the study of magnetic coupling phenomenon in a larger scale, especially The use of this long-range coupling mechanism, design and development of new high-performance permanent magnet materials less reported.Recently, Institute of Materials Science and Engineering, Chinese Academy of Sciences rare earth magnetic functional materials laboratory permanent magnetics research group, through the structural design of magnetic phase length Magnetic coupling, so as to achieve microscopic to macroscopic scale 'soft' and 'hard' composite, prepared with a new composite structure of high performance permanent magnet materials, and a good interpretation of rare earth permanent magnet system using short-range exchange coupling is difficult Explain the many magnetic problems.
In view of the small grain size of the original powder particles of the hot-deformed Nd-Fe-B magnet, the research team first used the permanent magnet powder rich in La, Ce and other high abundance rare earths to realize the interaction with the Nd- Fe-B powder, the high La and Ce hot-deformed magnets with excellent macro-magnetic properties were successfully prepared. When the maximum magnetic energy product
Up to 43.5MGOe, coercivity up to 1.07T; when 20wt.% Ce replaced, the maximum energy product
Up to 39.1MGOe, coercive force of 1.20T.
Following this work, the researchers used NdPr-Cu and Dy-Cu eutectic alloy diffusion techniques to prepare non-heavy rare earth high coercivity hot deformed Nd-Fe-B magnets with a macroscopic core-shell structure and Nd-Fe-B magnet with high magnetic energy and thermal deformation.The structure shows a unique gradient structure in terms of elemental distribution and grain size, with a gradient range of 2-6mm. However, the overall magnetic properties of the magnet are not affected by the macro - Shell 'structure and the emergence of a significant loss of the phenomenon of the opposite magnetic behavior showed good consistency, which proved from the millimeter scale magnet strong long-range magnetic coupling exists, as shown in Figure A, B.
To further verify and make use of this long-range coupling, the researchers selected two magnetic phases with significant differences in intrinsic magnetic properties and analyzed the multi-scale coupling between magnetic phases by means of macrostructure design. Based on the experiments, The optimal coupling distance between the two phases in the order of magnitude produces a hot deformed Nd-Fe-B magnet with excellent properties, as shown in Figs.
Through the magnetic properties and structural characterization under multi-scale conditions, it is revealed that the long-range magnetostatic coupling can break through the nanometer scale limitation and achieve good coupling effect in the range of micrometers or millimeters.This magnetic characteristic is to design and prepare a new type of high Performance thermal deformation of Nd-Fe-B material provides new ideas related research results have been published in Applied Physics Letters, Scientific Reports, Journal of Alloys and Compounds and Journal of Magnetism and Magnetic Materials, and apply for two national invention patents. The work has been supported by the national key research and development plan and the National Natural Science Foundation.
