Abstract
In this study, the factors influencing the nucleation of magnetic vortices in CeFeB ribbons were studied using Lorentz transmission electron microscopy. Magnetic vortices and cross-tie walls exist in Ce14Fe80B6 amorphous ribbons. Via proper annealing, the amorphous ribbon is crystallized into a nanocrystalline structure whereby a magnetic vortex can exist in grains with sizes of approximately 30∼150 nm, indicating the formation of magnetic vortices is closely related to shape limitation. Moreover, it has been demonstrated magnetic vortices are the intrinsic magnetic domain structures in the amorphous alloys due to their weak magnetocrystalline anisotropy. This study provides a way to promote magnetic vortex formation in the nanocrystalline structure.
Highlights
To understand the magnetic vortex formation, experimental and theoretical studies have been carried out,7–14 demonstrating that the magnetic vortex and anti-vortex can nucleate under the application of external fields
Magnetocrystalline anisotropy is usually absent in the amorphous alloys, a specific magnetic domain structure may occur in the amorphous sample due to the induced anisotropy and residual anisotropies mainly originating from internal stresses
In order to explore the effect of these factors on the nucleation of the magnetic vortex, we studied the magnetic vortex in samples with different crystalline states and compositions
Summary
Nanoscale magnetic domain structures, such as magnetic vortex, nontrivial bubble, and skyrmion, have attracted significant research interest because of underlying applications as basic units for spintronic devices. Among them, the magnetic vortex possesses a core of approximately 10 nm and usually appears in the materials exhibiting weak magnetic anisotropy, such as permalloy. The density and manipulation of magnetic vortices are of great significance to their potential applications. To understand the magnetic vortex formation, experimental and theoretical studies have been carried out, demonstrating that the magnetic vortex and anti-vortex can nucleate under the application of external fields. Previous research on the nucleation of magnetic vortices mainly concentrates on the patterned confinement structures of permalloy, where a relatively high external magnetic field/current density is usually required to manipulate these magnetic vortices, limiting their applications.. A recent study reveals that magnetic vortices can spontaneously form in amorphous CeFeB ribbon and can be manipulated by external fields, which is important to the potential applications. The present work aims to study magnetic vortices in amorphous and nanocrystalline ribbons by means of Lorentz transmission electron microscopy (LTEM) to reveal the key factors influencing magnetic vortex nucleation. When the amorphous ribbons become nanocrystalline structure after suitable annealing, magnetic vortices appear in grains with size about 30∼150 nm and will not be stable if the grains are too large or too small, indicating the formation of magnetic vortices is closely related to shape limitation. Magnetic vortices have been observed in other typical amorphous materials such as Fe50.77Co9.24Ni15.31Cu0.97Si11.89B8.55Nb3.1 and Fe78Si9B13, which may mean that magnetic vortices are the intrinsic magnetic domains in the amorphous alloys due to their weak magnetic anisotropy
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