Numerical simulation of a magnetostatically coupled composite magnet

Abstract

The demagnetization behavior of the hard-soft composite magnet has been simulated with a simple model in order to understand better the magnetization reversal of die-upset composite magnets fabricated from blends of Nd–Fe–B ribbons and coarse Fe powders. The calculations show that soft magnetic inclusions of any size can be fully magnetically coupled with the hard matrix by long-range magnetostatic interactions provided that the inclusions form layers perpendicular to the magnetization direction. Though the magnetostatic coupling along does not lead to enhanced hard magnetic properties of the composite magnets, it makes the full exchange coupling between the hard and soft phases unnecessary and, therefore, relaxes the strict requirements for the size of the soft inclusions. The combination of magnetostatic coupling and partial exchange coupling in a die-upset magnet with layered morphology may facilitate the development of anisotropic hard-soft composite magnets with properties superior to the single-phase permanent magnets.

Microstructural changes during the slow-cooling annealing of nanocrystalline SmCo 2:17 type magnets

“…As above mentioned, in previous studies, the isotropic samples presented remanence equal or lower the half the saturation [10,11]. Remanence lower than half the saturation may be caused by magnetostatic coupling [16]. However, for the sample presented at Fig.…”

Permanent magnetism of dense-packed nanostructures

“…The packing fraction of the hard-magnetic phase and other structural features affect the magnetic field inside and outside the magnet, and question arises whether there is any interference between nanoscale and macroscopic features and how they could be used to improve the performance of permanent magnets. [3][4][5][6] This also affects potential applications that use permanent magnets of reduced size, for example, in micromechanical devices and elements for spin electronics.…”

Magnetization reversal in textured NdFeB–Fe composites observed by domain imaging

“…In Ref. [5] the increase in remanence values with increasing Fe content has been explained by partially exchange coupling between the two phases. One possible reason for the deviation from our experiments is the Fe particle size, which is smaller in the case of samples presented in Ref.…”

“…The easy axis of magnetization, which is in the case of NdFeB consistent with the c-axis, is parallel to the pressing direction. Gabay et al [5] stated that the coupling effect between the two magnetic phases is due to magnetostatic interactions, which could also be supported by simple numerical simulations [5]. The single-phase behavior of these composites during demagnetization makes them interesting for detailed studies of the magnetic microstructure and its behavior in a magnetic field.…”