Materials World Network: Titanomagnetite Decomposition and Magnetic Sensors for Their Terrestrial and Extraterrestrial Observation.

材料世界网络：钛磁铁矿分解和用于陆地和外星观测的磁传感器。

• 批准号: 1106943
• 负责人: Michael McHenry
• 金额: $ 58.4万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1106943&HistoricalAwards=false
• 关键词: Materials; World; Network; Titanomagnetite; Decomposition

This effort, based on collaboration with the Instituto Nacional de Técnica Aeroespacial (INTA) in Madrid, Spain, examines the role of nanostructure on the temperature-dependent remanent magnetic state of spinodally decomposed two phase mixtures in the Fe2TiO4-Fe3O4 pseudo-binary titanomagnetite system. The pseudo-binary Fe2TiO4-Fe3O4 system is an interesting system for using magnetic measurements to probe the kinetics of phase transformations. This oxide system has a miscibility gap with spinodal decomposition. The two phases appearing in the decomposition are a strongly magnetic magnetite and a more weakly magnetic Ti-rich spinel. Many starting compounds in a homogeneous metastable solid solution are non-magnetic at temperatures where the decomposition kinetics can be monitored in reasonable experimental times. The magnetite formed by the decomposition reaction is magnetic at these temperatures and its magnetization is a measure of the volume fraction transformed. Time-dependent magnetization measurements are used to monitor the kinetics of spinodal decomposition for compositions within the spinodes and nucleation and growth kinetics for compositions outside of the spinodes. The investigators at Carnegie Mellon University (CMU) have developed synthesis routes for compounds in the pseudobinary Fe2TiO4-Fe3O4 system that allow to more accurately define the asymmetric miscibility gap in this system. The fine microstructure resulting from spinodal decomposition and exchange anisotropy mechanisms for coupling may explain a large slowly decaying remanent state for these minerals on Mars. The non-saturating behavior of Ti-rich spinels is hypothesized as arising from to non-collinear spins. The coupling of the spins in the ferrimagnetic magnetite in modulated spinodal structures is of interest. Certain compounds are of further interest because they have magnetic transitions that are within the day to night temperature swing on Mars and can therefore be detected with miniaturized magnetic sensors.The research also sheds light on the role of these minerals on terrestrial and extraterrestrial magnetic field anomalies and uses magnetic measurements as a probe of the kinetics of decomposition. The titanomagnetites offer a rich magnetic system to explore the role of fine microstructure on magnetic properties. They are important minerals in basalts and a commonly occurring mineral on the moon and Mars. Since both the moon and Mars lack an intense global magnetic field, magnetic mapping is even more powerful on these two bodies than on Earth. On Earth magnetic surveys are complicated by the presence of the main field, which makes measurements of crustal anomalies challenging and difficult to discern. The global magnetic mapping together with the study of the minerals of the crust and surface and their remanent state can give clues to the geomagnetic evolution of a planet. Miniaturized magnetic sensors are further developed at INTA, with support from the Spanish Ministry of Science and Innovation, based on magnetic films developed at CMU that allow the remanent magnetic state of extraterrestrial minerals to be studied within the natural day to night temperature swing on the Martian surface. These sensors are also made available for characterization of biomagnetic systems on Earth. The proposed research involves two shared Ph.D students and develops mechanisms for undergraduate student exchanges. Students will also attend an INTA summer school on "Mars and its Enigmas" held at INTA. A second "Small Magnetic Sensors and Sensor Materials" satellite meeting to the Magnetism and Magnetic Materials (MMM) Conference will be proposed to disseminate results.

这项工作基于与西班牙马德里国家航空航天研究所(INTA)的合作，研究了纳米结构对Fe2TiO4-Fe3O4伪二元钛磁铁矿系统中旋节分解的两相混合物随温度变化的剩余磁状态的作用。准二元系Fe2TiO4-Fe3O4体系是一种有趣的利用磁测量来探索相变动力学的体系。该氧化物体系具有与调幅节点分解的混溶间隙。分解过程中出现的两种相是强磁性磁铁矿和磁性较弱的富钛尖晶石。均相亚稳态固溶体中的许多起始化合物在温度下是非磁性的，在这种温度下，可以在合理的实验时间内监测分解动力学。分解反应形成的磁铁矿在这些温度下是磁性的，其磁化强度是转化的体积分数的量度。随时间变化的磁化测量被用来监测旋节内组合物的调幅分解动力学和旋节外组合物的成核和生长动力学。卡内基梅隆大学(CMU)的研究人员开发了伪二元Fe2TiO4-Fe3O4体系中化合物的合成路线，允许更准确地定义该体系中的不对称混溶间隙。由旋节分解和交换各向异性耦合机制产生的精细微结构可能解释了这些矿物在火星上大量缓慢衰变的残余状态。富钛尖晶石的非饱和行为被认为是由非共线自旋引起的。亚铁磁性磁铁矿中的自旋在调制调幅节状结构中的自旋耦合是令人感兴趣的。某些化合物更令人感兴趣，因为它们的磁相变在火星上白天到夜间的温度波动范围内，因此可以用微型磁传感器检测到。这项研究还揭示了这些矿物对地球和地外磁场异常的作用，并使用磁性测量作为分解动力学的探针。钛磁铁矿提供了丰富的磁性体系，以探索精细微结构对磁性能的影响。它们是玄武岩中的重要矿物，也是月球和火星上常见的矿物。由于月球和火星都缺乏强烈的全球磁场，因此在这两个天体上的磁测绘甚至比在地球上更强大。在地球上，磁力测量因主磁场的存在而变得复杂，这使得测量地壳异常具有挑战性和难以辨别。全球磁图与地壳和地表矿物及其残存状态的研究一起可以为行星的地磁演化提供线索。在西班牙科学和创新部的支持下，INTA进一步开发了微型磁性传感器，该传感器基于CMU开发的磁性薄膜，可以在火星表面自然昼夜温度波动范围内研究外星矿物的剩余磁性状态。这些传感器也可用于描述地球上的生物磁系统。这项拟议的研究涉及两名共享博士生，并开发了本科生交流机制。学生们还将参加在INTA举办的关于“火星及其谜团”的暑期班。将提议在磁性和磁性材料会议上召开第二次“小型磁性传感器和传感器材料”卫星会议，以传播成果。