Modeling of Intergrain Exchange Coupling for Quantitative Predictions of $delta m$ Plots
Modeling of Intergrain Exchange Coupling for Quantitative Predictions of $delta m$ Plots
复制标题
用于 $delta m$ 图定量预测的粒间交换耦合建模
DOI：
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发表时间：
2010
影响因子：
2.1
通讯作者：
L. Schultz
中科院分区：
文献类型：
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作者：
V. Neu;R. Biele;Aarti Singh;L. Schultz
通过δ m图研究不可逆开关过程是评估纳米磁性材料晶粒间相互作用的常用实验技术。另一方面，关于晶粒尺寸、结构和磁场方向对δ m图的形状和绝对值的影响的理论预测却缺失了。在本文中，直接晶间交换耦合的两个耦合，硬磁颗粒的模型系统的数值/分析相结合的方法进行评估。定量确定了晶粒尺寸和易轴取向对δ m分析结果的影响。正如直接交换耦合的短程特性所预期的那样，场积分δ m信号随着晶粒尺寸的增加而减小。然而，尽管具有平行易轴取向的直接耦合晶粒具有大的正δm值，但随着取向差角的增加，积分δ m信号减小，甚至达到负值。这种负δm效应迄今为止只与间接静磁相互作用有关。在该模型的统计扩展，与高斯分布的纹理轴沿沿着一个定义良好的样品方向的晶粒系综进行检查。的形状，宽度和高度的计算δ m-图承担已知的纳米晶，织构良好的SmCo 5薄膜的实验研究的特征。
The study of irreversible switching processes via δm-plots is a common experimental technique to assess intergrain interactions in nanoscaled magnetic materials. Theoretical predictions, on the other hand, of the influence of grain size, texture and field direction on the shape and absolute values of δm-plots are missing. In this paper direct intergrain exchange coupling is evaluated in a combined numerical/analytical approach for a model system of two coupled, hard magnetic grains. The influence of grain size and easy axis orientation on the outcome of a δm-analysis is determined quantitatively. As expected from the short range characteristic of direct exchange coupling, the field-integrated δm-signal decreases with increasing grain size. However, whereas directly coupled grains with parallel easy axis orientation possess large positive δm -values, for increasing misorientation angle the integrated δm-signal reduces and reaches even negative values. Such an effect of negative δm is so far only associated with indirect magnetostatic interactions. In a statistical extension of the model, grain ensembles with Gaussian distribution of their texture axis along one well defined sample direction are examined. The shape, width and height of the calculated δm-plots bear characteristic features known from experimental studies on nanocrystalline, well textured SmCo5 films.