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

非晶态的Fe-Nb-Cu-Si-B纳米晶带在拉应力作用下晶化，产生磁各向异性，获得了极低的损耗和可控的磁导率。对各向异性的诱导和松弛过程的研究表明，各向异性是在晶化过程中诱导的。因此，通过控制S在晶化过程中的退火工艺，各向异性得到了很大的改善。在所研究的几种方法中，通过缠绕晶化后的带材形成环状磁芯的方法获得了最优的磁性能。因此，我们对这种方法进行了详细的研究。磁损耗随磁芯直径的增大而减小，并发现通过使磁芯直径大于由磁致伸缩和感应各向异性确定的临界直径，可以抑制由于形成环形磁芯而导致的磁性能恶化。结果，得到了损耗极低的环形磁芯。研制的磁芯的磁导率在1 MHz以下保持恒定，其磁损耗值远小于先前报道的低磁导率的纳米结构和非晶态磁芯的损耗值。测得的磁损耗与经典涡流损耗的计算值相吻合。此外，磁导率和磁损耗保持不变，直到直流偏置磁场比相同磁导率的铁氧体切割磁芯高出三倍。

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.