Critical single-domain grain sizes in elongated iron particles: implications for meteoritic and lunar magnetism
Critical single-domain grain sizes in elongated iron particles: implications for meteoritic and lunar magnetism
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DOI：
10.1093/gji/ggv180
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发表时间：
2015-07-01
影响因子：
2.8
通讯作者：
Williams, Wyn
中科院分区：
文献类型：
--
作者：
Muxworthy, Adrian R.;Williams, Wyn
鹰嘴石颗粒(Fe-Ni，Ni<；5%)在陨石等地外物质中非常常见。通常认为，对于可靠的磁场记录器，铁氰酸钾颗粒需要具有均匀的磁性(单磁区，SD)和热稳定性。较大的粒子细分为产生较弱磁信号的非均匀多域(MD)磁性结构，而较小的SD粒子由于热波动而变得磁性不稳定，并表现出超顺磁性行为。本文首次确定了金属铁稳定SD域态相图的微磁学计算，以前的计算都是解析式的。SD/MD阈值尺寸的临界尺寸显著增加，例如，对于立方体形状的铁颗粒，临界SD/MD阈值现在被估计为25 nm，而以前的估计为17 nm。较大的铁的临界SD/MD阈值尺寸，与先前发表的FeNi粒子的磁畴状态的纳米观测结果更符合，而不是早期的分析模型。
Kamacite particles (Fe-Ni, Ni < 5 per cent), are very common in extra-terrestrial materials, such as meteorites. It is normally assumed that for kamacite particles to be reliable recorders of magnetic fields, they need to be magnetically uniform (single domain, SD) and thermally stable. Larger particles subdivide into non-uniform multidomain (MD) magnetic structures that produce weaker magnetic signals, while small SD particles become magnetically unstable due to thermal fluctuations and exhibit superparamagnetic behaviour. In this paper we determine the first micromagnetic calculation of the stable SD range domain-state phase diagram for metallic iron; previous calculations were analytical. There is a significant increase in the critical size for the SD/MD threshold size, for example, for cube-shaped iron particles, the critical SD/MD threshold has now been estimated to be 25 nm, compared to 17 nm for previous estimates. The larger critical SD/MD threshold size for iron, agrees better with previously published nanometric observations of domain state for FeNi particles, then early analytical models.