Real picture of magnetic domain dynamics along the magnetic hysteresis curve inside an advanced permanent magnet

Abstract

In the long history of permanent magnet research for more than 100 years, three-dimensional magnetic microscopy has been eagerly awaited to elucidate the origin of the magnetic hysteresis of permanent magnets. In this study, we succeeded in observing the three-dimensional magnetic domain structure of an advanced high-coercivity Nd-Fe-B-based permanent magnet throughout the magnetic hysteresis curve using a recently developed hard X-ray magnetic tomography technique. Focused-ion-beam-based three-dimensional scanning electron microscopy was employed to study the relationship between the observed magnetic domains and the microstructure of the magnet for the same observing volume. Thermally demagnetized and coercivity states exhibit considerably different magnetic domain structures but show the same periodicity of 2.3 μm, indicating that the characteristic length of the magnetic domain is independent of the magnetization states. Further careful examination revealed some unexpected magnetic domain behaviors, such as running perpendicular to the magnetic easy axis and reversing back against the magnetic field. These findings demonstrate a wide variety of real magnetic domain behaviors along the magnetic hysteresis inside a permanent magnet.

Laser-beam powder bed fusion of magnetostrictive Fe81Ga19 alloys: parameter optimization, microstructural evolution and magnetostrictive properties

“…Moreover, it was clearly observed from the corresponding enlargement (figure 5(d)) that a small coercivity value (Hc) of 15 Oe and extremely narrow loop, i.e., extremely low hysteresis, exhibiting typical soft magnetic behavior. As we known, the hysteresis effect exists in the dynamic magnetization process accompanying the magnetic domain rotation and domain wall movements, which is associated with magnetic domain structure, grain structure, defect and so on [67,68]. In the present study, the motion of magnetic domains in the LPBF-prepared Fe 81 Ga 19 alloys would be hindered by grain boundaries and defects such as dislocations and pores, which probably caused by high energy impact and rapid solidification of LPBF process, during the magnetization process.…”

Observation of Magnetic Domains in Amorphous Magnetic Wires with a Diameter of 10 μm Used in GSR Sensors

“…In this study, observations of magnetic domains were performed at the polished surface of an amorphous magnetic wire. Further investigations, such as three-dimensional magnetic domain observations [ 32 , 33 , 34 , 35 , 36 ], are needed to clarify the effect of polishing on the magnetic domain structure. In the future, it would be desirable to experimentally measure the noise of the GSR sensor and compare it directly with the changes of the magnetic domain structure.…”

One-pot synthesis of NiFe nanoarrays under an external magnetic field as an efficient oxygen evolution reaction catalyst

“…4f and S10 †), revealing that the synthesized materials have ferromagnetic properties. 41,42 The results show that MIL-53(Fe-Ni)/NF-2200Gs has the highest saturation value of z 47.45 emu g −1 than that of MIL-53(Fe-Ni)/NF-4400Gs (z45.80 emu g −1 ) and MIL-53(Fe-Ni)/NF-0 (z45.14 emu g −1 ). According to the previous reports, electron spin polarization could enhance the catalytic activity of OER, because the unique OER steps from singlet reactant to the triplet product ([O]O[) call for a spin-selective electron transfer.…”