Magnetic viscosity, diffusion after-effect, and disaccommodation in natural and synthetic samples.
Magnetic viscosity, diffusion after-effect, and disaccommodation in natural and synthetic samples.
复制标题
天然和合成样品中的磁粘度、扩散后效应和失调。
DOI：
10.1111/j.1365-246x.1985.tb05133.x
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发表时间：
1985
影响因子：
2.8
通讯作者：
B. Moskowitz
中科院分区：
文献类型：
--
作者：
B. Moskowitz
摘要：对来自国际大洋钻探计划（IPOD）417D站点的一些大洋玄武岩的磁黏滞性进行了研究。这些样品包括细粒枕状玄武岩和粗粒块状岩流。对这些样品黏滞行为的实验包括：（1）弱场黏滞剩磁（VRM）的获得和衰减；（2）交变磁场退磁后零场存储时间对VRM产生的影响。在所有情况下，发现VRM的获得都比其随后的衰减更快。观察到VRM强度的时间依赖性在获得过程中明显是非对数的，但在衰减过程中则不那么明显。样品在退磁后处于零场的时间长度会导致VRM的获得和衰减系数降低。这些结果无法完全与基于现有热涨落磁黏滞性模型的预测相吻合。现有证据还表明，（1）退磁后零场存储或（2）不同的初始磁化状态对VRM产生的影响归因于磁化率的减落。不幸的是，现有数据不足以完全确定扩散后效和减落对长期黏滞行为的重要性。然而，有人认为，在大洋中脊附近年轻的枕状玄武岩（<0.1百万年）中，扩散过程可能对VRM有贡献，因为钛磁铁矿的氧化会增加八面体晶格空位的数量，而地壳的高温会促进这些空位和亚铁离子的扩散重排。为了对VRM有更多的了解并试图解释其中的一些观测结果，对磁性材料中扩散后效和减落的理论和实验结果进行了综述。
Summary. The magnetic viscosity of some oceanic basalts from IPOD site 417D is investigated. The samples are fine-grained pillow basalts and coarse-grained massive flows. Experiments on the viscous behaviour of these samples include (1) acquisition and decay of weak-field viscous remanent magnetization (VRM) and (2) the influence on VRM produced by the zero field storage time following demagnetization by an alternating magnetic field. In all cases the aquisition of VRM is found to be more rapid than its subsequent decay. The time dependence of the intensity of VRM is observed to be significantly non-logarithmic during acquisition, but less so during decay. The length of time a sample remains in zero field following demagnetization produces a decrease in the aquisition and decay coefficients of VRM. These results cannot be reconciled entirely with predictions based on existing models of magnetic viscosity due to thermal fluctuations. Available evidence also suggest that the effect on VRM produced by (1) zero field storage following demagnetization or produced by (2) different initial states of magnetization, is attributed to susceptibility disaccommodation. Unfortunately, the available data are insufficient fully to ascertain the importance of diffusion after-effect and disaccommodation to long-term viscous behaviour. It is suggested, however, that diffusional processes may contribute to VRM in young pillow basalts (< 0.1 Ma) near mid-ocean ridges where the oxidation of titanomagnetite produces an increase in the number of octahedral lattice site vacancies and the elevated temperature of the crust enhances the diffusive reordering of these vacancies and ferrous ions. In order to gain some additional insights into VRM and attempt to explain some of these observations, theoretical and experimental results pertaining to diffusion after-effect and disaccommodation in magnetic materials are reviewed.