Edinburgh Research Explorer Stability of equidimensional pseudo-single-domain magnetite over billion-year timescales
Edinburgh Research Explorer Stability of equidimensional pseudo-single-domain magnetite over billion-year timescales
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对古地磁观测的解释假设自然产生的磁性粒子可以在数十亿年的时间内保留其原始磁记录。保留磁记录的能力是根据实验室测量推断的，其中加热会导致大约几秒的消磁。这一推论的理论基础来自于之前的模型，这些模型假设只存在小的、均匀磁化的粒子，而岩石中古地磁信号的载体通常是较大的、非均匀磁化的粒子，对此没有经验上完整的热激活模型。这项研究开发了一种热激活数值微磁模型，可以定量确定地质时间尺度上非均匀磁性粒子稳定状态之间的能量势垒。我们详细研究了等维立方八面体磁铁矿的热稳定性特征，发现与之前发表的理论相反，这种非均匀磁化颗粒比均匀磁化颗粒提供了更高的磁稳定性。因此，非均匀磁化颗粒通常是陨石和岩石中的主要剩磁载体，可以记录并保留数十亿年的高保真磁记录。
Interpretations of paleomagnetic observations assume that natu-rally occurring magnetic particles can retain their primary magnetic recording over billions of years. The ability to retain a magnetic recording is inferred from laboratory measurements, where heating causes demagnetization on the order of seconds. The theoretical ba-sis for this inference comes from previous models that assume only the existence of small, uniformly magnetized particles, whereas the carriers of paleomagnetic signals in rocks are usually larger, non-uniformly magnetized particles, for which there is no empirically complete, thermally-activated model. This study has developed a thermally-activated numerical micromagnetic model that can quanti-tatively determine the energy barriers between stable states in non-uniform magnetic particles on geological time scales. We examine in detail the thermal stability characteristics of equidimensional cuboctahedral magnetite and find that contrary to previously published theories, such non-uniformly magnetized particles provide greater magnetic stability than their uniformly magnetized counterparts. Hence, non-uniformly magnetized grains, which are commonly the main remanence carrier in meteorites and rocks, can record and retain high-fidelity magnetic recordings over billions of years.