In situ magnetic force microscope studies of magnetization reversal of interaction domains in hot deformed Nd-Fe-B magnets

Abstract

A hot-deformed Nd-Fe-B sample has been chosen for the investigation of interaction domains by means of magnetic force microscopy. During the imaging process, a magnetic field of up to 6 T was applied in situ along the easy axis of magnetization. The thermally demagnetized state presents a regular pattern of interaction domains with an average width of about 1 μm but with a much larger length scale. Starting from the thermally demagnetized state, magnetization along the initial magnetization curve occurs via sequential switching of neighboring grain columns at the peripheries of the interaction domains. Demagnetization of a saturated sample takes place through the nucleation and expansion of a patchy domain pattern with a much larger extension and a substructure in the lateral range of the underlying grain size. Reversal processes under an applied magnetic field also take place at the borders of the domains.

Employing soft x-ray resonant magnetic scattering to study domain sizes and anisotropy in Co/Pd multilayers

“…A second difference is the increase of frequency at very small domain sizes. This is discussed in [43] as a consequence of wavy domain walls specific to this system, a feature we do not observe in our Co/Pd films. For this example it is clear that the domain size distribution of the two-dimensional maze pattern is fairly well described by a one-dimensional gamma distribution.…”

“…2(b) in Ref. [43]) yields a strongly asymmetric distribution of domain sizes which is at variance with a symmetric Gaussian peak shape. The distribution falls off faster towards small domain sizes and extends wider towards large domains.…”

“…To justify such a model, we have compared a published domain size distribution of a maze pattern with a gamma distribution. Thielsch et al [43] have analyzed a Kerr microscopy image of a Nd-Fe-B sample by taking line profiles along different directions and measuring the distances between domain walls. This analysis (reproduced in Fig.…”

Micromagnetic simulation for the magnetization reversal process of Nd-Fe-B hot-deformed nanocrystalline permanent magnets

“…2(c), which cannot be reproduced in the previous study. 18 To clarify the details of the anisotropic propagation of the reversal magnetic domain, we show the propagation of the magnetization reversal in grains selected from simulation model. These grains were connected in the xy plane and overlapped with each other along the z direction.…”

Relationship Between Bulk Coercivity and Coercivity of Surface Layer in Nd-Fe-B-Based Sintered Magnet

“…The coercivity of a Nd-Fe-B -based magnet is greatly changed not only by the addition of Dy and Tb but also by the microstructure. To understand directly the relationship between the microstructure and magnetic domain structure in the magnet, several methods for evaluating the magnetic domain structure on the surface of the magnet are studied, such as the magneto-optical Kerr microscope 1,2) , magnetic force microscope (MFM) 3,4) and spin-polarized scanning electron microscope (spin-SEM) 5,6) . However, on a polished surface of a Nd-Fe-B-based magnet, magnetization reversal progresses with a clearly smaller magnetic field than the bulk coercivity.…”