Development of magnetic cores with extremely loss and controllable permeability using creep-induced ansisotropy

在拉伸应力作用下，非晶薄带由非晶转变为非晶，从而在Fe-Nb-Cu-Si-B纳米晶薄带中诱导出磁各向异性，获得了极低的损耗和可控的磁导率。对各向异性的诱导和弛豫过程的研究表明，各向异性是在晶化过程中诱导产生的。因此，通过控制晶化过程中的退火过程，可以在很大程度上改善各向异性。随后，研究了利用已开发的带制备环形磁芯的方法。在研究的几种方法中，通过在晶化后缠绕带形成环形磁芯获得了最优越的上级磁性能。因此，我们详细研究了这种方法。磁损耗随着芯直径的增加而降低，并且发现通过使芯直径大于由磁致伸缩和感生各向异性的值确定的临界直径，抑制了由于形成环形芯而导致的磁性能的劣化。结果，实现了具有极低损耗的环形磁芯。所开发的磁芯的磁导率保持恒定至1 MHz，并且它们的磁损耗远小于先前报道的具有低磁导率的纳米结构和非晶磁芯的损耗值。测量的磁损耗与计算的经典涡流损耗一致。此外，磁导率和磁损耗保持恒定的直流偏置场是三倍高于适用于具有相同磁导率值的铁氧体切割芯。

Magnetic anisotropy was induced to Fe-Nb-Cu-Si-B nanocrystalline ribbons by ciystallizing amorphous ribbons from the amorphous state under tensile stress, and extremely low loss and controllable permeability were achieved in them. Investigations on the induction and relaxation processes of the anisotropy revealed that the anisotropy is induced during the crystallization. Thus, the anisotropy was improved in magnitude by controlling the annealing proces s during crystallization.Subsequently, the methods of preparing toroidal cores from developed ribbons was studied. Among several methods investigated, the formation of a toroidal core by winding the ribbons after crystallization achieved the most superior magnetic properties. Therefore, we investigated this method in detail. The magnetic loss decreased with increasing the core diameter and it was found that deterioration of magnetic properties due to formation of a toroidal core was suppressed by making the core diameter larger than the critical diameter determined from the values of magnetostriction and induced anisotropy. Resultantly, toroidal cores with extremely low loss were achieved. The permeability of the developed cores was kept constant up to 1 MHz and their magnetic loss was much smaller than the loss values reported previously for nanostructured and amorphous cores with low permeability. The measured magnetic loss agreed with the calculated classical eddy current loss. In addition, the permeability and magnetic loss were kept constant up to the DC-bias field being three times higher than that applicable to a ferrite cut-core with the same permeability value.