How pressure influences the magnetic properties of titanomagnetite and iron with implications for magnetic anomalies and core fields

压力如何影响钛磁铁矿和铁的磁性，并对磁异常和核心场产生影响

• 批准号: 170001569
• 负责人: Professor Dr. Stuart Alan Gilder
• 金额: --
• 依托单位: Bayerisches Forschungsinstitut für Experimentelle Geochemie und Geophysik (BGI)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/170001569?language=en
• 关键词: How; pressure; influences; magnetic; properties

Pressure is an important variable in the Earth and planetary sciences, yet little is known abouthow extreme pressures influence the magnetic properties of geomaterials. Such knowledge isimportant to properly interpret magnetic anomalies and to understand how iron or iron alloys inthe solid inner core of planets interact with the magnetic fields generated in their outer cores. Wepropose to develop new high-pressure cell technology that allows us to directly measure the fullmagnetic vector of well-characterized samples as a function of pressure and temperature. Ourexperiments are intended to better understand pressure-induced changes in Curie temperatureand magnetic moment of relevant magnetic remanence carriers such as titanomagnetite andiron, including iron phases with Ni and S, with particular relevance to the cores of Earth, Marsand potentially Mercury. Numerical modelling will compliment the experiments by computingstructural and magnetic phase diagrams of iron and Fe-Ni/S alloys. The thermodynamicparameters will in part be fit to ab-initio phase diagram computations based on the clusterexpansion formalism. Magnetic ordering temperatures will be computed in the Fe and the Fe-Ni/S systems by evaluating Heisenberg Hamiltonians in the mean-field-approach and randomphase-approximation. Exchange interaction parameters for the Heisenberg Hamiltonians will beobtained by fitting ab-initio computations on magnetic structures.

压力是地球和行星科学中的一个重要变量，但人们对极端压力如何影响地质材料的磁性却知之甚少。这些知识对于正确解释磁异常以及了解行星固体内核中的铁或铁合金如何与其外核中产生的磁场相互作用非常重要。我们建议开发新的高压池技术，使我们能够直接测量表征良好的样品的全磁矢量作为压力和温度的函数。我们的实验旨在更好地了解压力引起的相关剩磁载体（例如钛磁铁矿和铁）的居里温度和磁矩的变化，包括含镍和硫的铁相，特别与地球、火星和潜在水星的核心相关。数值模型将通过计算铁和 Fe-Ni/S 合金的结构和磁性相图来补充实验。热力学参数将部分适合基于簇扩展形式主义的从头算相图计算。将通过在平均场方法和随机相位近似中评估海森堡哈密顿量来计算 Fe 和 Fe-Ni/S 系统中的磁有序温度。海森堡哈密顿量的交换相互作用参数将通过对磁结构进行从头计算拟合来获得。