Npj Comput. Mater.: 软磁材料的高效设计

新型软磁材料可用于快速能量转换电子器件、电动汽车和风力涡轮机等领域，理解与设计低矫顽力软磁材料具有十分重要的意义。然而，材料科学界长期存在的一个难题是如何理解铁磁材料中磁滞的起源。这里的磁滞是指当磁场增加至饱和时与磁场从饱和降至零时，退磁样品的不同行为，磁场的最终值被称为矫顽力。通常，软磁材料的矫顽力很低，这对自旋电子和存储设备至关重要。目前，一种被广泛采用的降低铁磁合金中磁滞的方法，是通过改变合金的组分以降低磁各向异性常数 κ1，从而减小合金的矫顽力。这个策略虽然取得了不少成功，但依旧存在许多问题亟待解决。比如，在铁镍体系中，随着组分变化会存在矫顽力的突变；在铁硅铝合金中，最小磁滞仅是在磁晶各向异性和磁致伸缩常数接近于零是才能出现；Galfenol合金的磁晶各向异性常数非常大，但磁滞却很小。这例子说明磁晶各向异性常数不是决定磁滞的唯一因素。

来自南加州大学和明尼苏达大学航空-机械工程学院的Balakrishna教授与James教授合作，利用他们近期开发的微磁模型，提出了一种可用于设计具有极低磁滞的铁磁材料的策略，并且能利用矫顽力进行量化。研究发现，磁滞的大小取决于传统的磁晶各向异性和磁致伸缩常数。他们定量地证明了在降低磁矫顽力过程中，磁晶各向异性系数、磁致伸缩常数和尖峰域微观结构（局部扰动）三者之间的微妙平衡至关重要。基于此，作者提出了在<100>易磁化立方铁磁体系中，设计较小矫顽力材料的参数依赖关系：(c11−c12)λ2100/(2κ1)=81。这些研究结果不仅拓展了人们对磁滞影响因素的理解，为磁性合金矫顽力的降低提供理论指导。该研究有望为能源研究领域中自旋电子与储能等器件方面提供候选磁性材料。

该文近期发表于npj Computational Materials 8, 4 (2022)，英文标题与摘要如下：

Design of soft magnetic materials
Ananya Renuka Balakrishna & Richard D. James 

We present a strategy for the design of ferromagnetic materials with exceptionally low magnetic hysteresis, quantified by coercivity. In this strategy, we use a micromagnetic algorithm that we have developed in previous research and which has been validated by its success in solving the “Permalloy Problem”—the well-known difficulty of predicting the composition 78.5% Ni of the lowest coercivity in the Fe–Ni system—and by the insight it provides into the “Coercivity Paradox” of W. F. Brown. Unexpectedly, the design strategy predicts that cubic materials with large saturation magnetization ms and large magnetocrystalline anisotropy constant κ1 will have low coercivity on the order of that of Permalloy, as long as the magnetostriction constants λ100, λ111 are tuned to special values. The explicit prediction for a cubic material with low coercivity is the dimensionless number (c11−c12)λ2100/(2κ1) = 81(c11−c12)λ1002/(2κ1) = 81 for〈100〉easy axes. The results would seem to have broad potential application, especially to magnetic materials of interest in energy research.

转自：知社学术圈

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