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

在地球和行星科学中，压力是一个重要的变量，但人们对极端压力如何影响地质材料的磁性知之甚少。这些知识对于正确解释磁异常和理解行星固体内核中的铁或铁合金如何与外核产生的磁场相互作用是很重要的。我们建议开发新的高压电池技术，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理解压力引起的居里温度和相关磁剩余物载体（如钛磁铁矿和铁铁矿）的磁矩变化，包括具有Ni和S的铁相，特别是与地球，火星和潜在的水星的核心相关。数值模拟将通过计算铁和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于基于簇展开形式的从头计算相图。通过平均场法和随机相位近似的海森堡-哈密顿量计算铁和铁- ni /S体系的磁有序温度。海森堡哈密顿量的交换相互作用参数将通过对磁性结构的从头计算拟合得到。

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.