Exceptionally High Saturation Magnetic Flux Density and Ultralow Coercivity via an Amorphous–Nanocrystalline Transitional Microstructure in an FeCo‐Based Alloy

Abstract

High saturation magnetic flux density (Bs) of soft magnetic materials is essential for increasing the power density of modern magnetic devices and motor machines. Yet, increasing Bs is always at the expense of high coercivity (Hc), presenting a general trade‐off in the soft magnetic material family. Here, superior comprehensive soft magnetic properties, i.e., an exceptionally high Bs of up to 1.94 T and Hc as low as 4.3 A m−1 are unprecedentedly combined in an FeCo‐based alloy. This alloy is obtained through a composition design strategy to construct a transitional microstructure between amorphous and traditional nanocrystalline alloys, with nanocrystals (with < 5 nm‐sized crystal‐like regions around) sparsely dispersed in an amorphous matrix. Such transitional microstructure possesses extremely low magnetic anisotropy caused by the annihilation of quasi‐dislocation dipoles, and a strong magnetic exchange interaction, which leads to excellent comprehensive magnetic properties. The results provide useful guidelines for the development of the next generation of soft magnetic materials, which are promising for applications of high‐frequency, high‐efficiency, and energy‐saving devices.

Critical state-induced emergence of superior magnetic performances in an iron-based amorphous soft magnetic composite

“…The fine nanocrystals are also ascertained to be α-Fe(Si) from the SAED pattern (figure 2(d)) and HRTEM image (figure 2(e)). It is noteworthy that a pair of diffraction spots within the first ring, weaker in intensity than sharp spots from bcc spots, can also be observed, which is consistent with the result of [19]. This observation suggests the existence of some MROs in the amorphous matrix [37], which generally ranges from 0.5-2 nm for amorphous alloys [38].…”

“…This observation suggests the existence of some MROs in the amorphous matrix [37], which generally ranges from 0.5-2 nm for amorphous alloys [38]. Typical MROs in the Fe-based amorphous alloys are reported as a kind of CLOs, playing an important role in tuning mechanical and soft magnetic properties [19,39,40].…”

“…On one hand, the avoidance of nanocrystals overcame the fatal disadvantage of harsh nucleation-growth processes in unfavorable amorphous systems [30]. On the other hand, the introduction of massive CLOs with α-Fe features improved the soft magnetic properties [19].…”

“…Improving the intrinsic soft magnetic properties of amorphous powders provides another way to achieve the synergy of magnetization and magnetic softness. Recently, a novel strategy to construct an amorphous nanocrystalline transitional microstructure between amorphous and traditional nanocrystalline alloys was proposed to overcome the trade-off between saturation magnetic induction (B s ) and H c [19]. However, because of the absence of nucleation element (Cu) and large atoms (Nb, Mo and V, etc.)…”

The influence of reaction temperature and surfactant on the magnetic and catalytic properties of FeCo nanoparticles

“…It could be seen from the image that the M s increased with the addition of surfactant, while the H c was just the opposite. In ferromagnetic FeCo nanoparticles, the exchange interaction was positive (Li et al 2022). The addition of surfactant induced repulsive forces which resulted in the formation of uniform small FeCo nanoparticles.…”