The hysteresis loops of nucleation-type magnets made of exchange-decoupled grains (i.e., sintered Nd–Fe–B magnets) reflect the discrete character of magnetization switching in such materials. Due to this discrete character, the experimental determination of coercivity depends on the measurement protocol. Finite element modeling allows us to investigate how the pattern of reversed grains develops during sample demagnetization performed under closed-circuit conditions, provided that the basic features of the hysteresigraph are known. Numerical modeling provides a quantitative understanding of the collective effects that are very pronounced in the closed-circuit configuration and shows how they affect both the slope of the demagnetizing curve and the sample coercivity. With a grain coercive field standard deviation adjusted to 0.1 T, it is numerically found that the difference in coercivity between closed- and open-circuit configurations is 40 kA/m, in good agreement with previous experimental data.The hysteresis loops of nucleation-type magnets made of exchange-decoupled grains (i.e., sintered Nd–Fe–B magnets) reflect the discrete character of magnetization switching in such materials. Due to this discrete character, the experimental determination of coercivity depends on the measurement protocol. Finite element modeling allows us to investigate how the pattern of reversed grains develops during sample demagnetization performed under closed-circuit conditions, provided that the basic features of the hysteresigraph are known. Numerical modeling provides a quantitative understanding of the collective effects that are very pronounced in the closed-circuit configuration and shows how they affect both the slope of the demagnetizing curve and the sample coercivity. With a grain coercive field standard deviation adjusted to 0.1 T, it is numerically found that the difference in coercivity between closed- and open-circuit configurations is 40 kA/m, in good agreement with previous experimental data.

中文翻译：

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在闭路几何中测量的永磁体退磁过程建模

由交换解耦晶粒（即烧结 Nd-Fe-B 磁体）制成的成核型磁体的磁滞回线反映了此类材料中磁化转换的离散特性。由于这种离散特性，矫顽力的实验确定取决于测量协议。有限元建模使我们能够研究在闭路条件下进行的样品退磁过程中反向晶粒的图案是如何发展的，前提是磁滞图的基本特征是已知的。数值建模提供了对闭路配置中非常明显的集体效应的定量理解，并显示了它们如何影响退磁曲线的斜率和样品矫顽力。将晶粒矫顽场标准偏差调整为 0.1 T，从数值上发现，闭路和开路配置之间的矫顽力差异为 40 kA/m，与之前的实验数据非常吻合。 由交换解耦晶粒（即烧结 Nd）制成的成核型磁体的磁滞回线–Fe–B 磁体）反映了此类材料中磁化转换的离散特性。由于这种离散特性，矫顽力的实验确定取决于测量协议。有限元建模使我们能够研究在闭路条件下进行的样品退磁过程中反向晶粒的图案是如何发展的，前提是磁滞图的基本特征是已知的。数值建模提供了对闭路配置中非常明显的集体效应的定量理解，并显示了它们如何影响退磁曲线的斜率和样品矫顽力。将晶粒矫顽场标准偏差调整为 0.1 T，从数值上发现闭路和开路配置之间的矫顽力差异为 40 kA/m，与之前的实验数据非常吻合。