Isothermal remanent magnetization (IRM) curves are used widely in rock magnetic and environmental magnetic studies to characterize magnetic properties of natural samples. Previous theoretical and experimental investigations indicate that magnetostatic interactions can strongly affect the IRM behavior. In order to quantitatively investigate this effect, we modeled IRM curves and hysteresis properties for magnetite assemblages with variable morphologies (grain size, elongation, and shape) using the finite-element micromagnetic modeling code MERRILL. We also conducted an analytical study of IRM behavior for noninteracting single domain grains utilizing the Stoner–Wohlfarth model. It is found that multiple Gaussian components do not necessarily reflect multiple magnetic mineral populations. For example, magnetostatic interactions can produce coercivity distributions that resemble results of some samples containing a detrital and extracellular (D + EX) and a biogenic soft or hard (BS/BH) coercivity components. Simulated IRM curves for different morphologies of interacting flattened grains are similar, indicating that the effect of interactions can overshadow the effect of grain morphologies. Moreover, our micromagnetic and analytical calculations consistently indicate that the IRM curves for noninteracting fine-grained assemblages are mostly determined by grain shape (elongated or flattened) and elongation distributions of the magnetic mineral assemblages. Our simulations present possible outcome of IRM curves for magnetic mineral assemblages with controlled grain size, shape and microstructures, which provides important theoretical constraints on characterizing complex magnetic mineral components in natural samples through IRM curves and hysteresis.

中文翻译：

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静磁相互作用对等温剩磁曲线影响的微磁计算：对磁性矿物识别的影响

等温剩磁 (IRM) 曲线广泛用于岩石磁性和环境研究，以表征天然样品的磁性。先前的理论和实验研究表明，静磁相互作用可以强烈影响 IRM 行为。为了定量研究这种影响，我们使用有限元微磁建模代码 MERRILL 对具有可变形态（晶粒尺寸、伸长率和形状）的磁铁矿组合的 IRM 曲线和磁滞特性进行建模。我们还利用 Stoner-Wohlfarth 模型对非相互作用单畴晶粒的 IRM 行为进行了分析研究。发现多个高斯分量不一定反映多个磁性矿物种群。例如，静磁相互作用可以产生矫顽力分布，类似于一些含有碎屑和细胞外 (D + EX) 以及生物软或硬 (BS / BH) 矫顽力成分的样品的结果。相互作用的扁平晶粒的不同形态的模拟 IRM 曲线相似，表明相互作用的影响可以掩盖晶粒形态的影响。此外，我们的微磁和分析计算一致表明，非相互作用细粒组合的 IRM 曲线主要由磁性矿物组合的晶粒形状（拉长或扁平）和伸长率分布决定。我们的模拟展示了具有受控粒度、形状和微观结构的磁性矿物组合的 IRM 曲线的可能结果，