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

这项工作的基础上，与西班牙马德里的国家航空航天技术研究所（INTA）的合作，探讨了纳米结构对Fe 2 TiO 4-Fe 3 O 4伪二元钛磁铁矿系统中旋节分解两相混合物的温度依赖性剩磁状态的作用。赝二元系Fe_2TiO_4-Fe_3O_4是一个有趣的系统，使用磁性测量来探测相变动力学。该氧化物体系具有与亚稳分解的相容性间隙。在分解过程中出现的两相是强磁性磁铁矿和较弱磁性的富钛尖晶石。在均匀亚稳固溶体中的许多起始化合物在可以在合理的实验时间内监测分解动力学的温度下是非磁性的。由分解反应形成的磁铁矿在这些温度下是磁性的，并且其磁化强度是转化的体积分数的量度。时间相关的磁化测量被用来监测的spinode内的组合物的spinodal分解的动力学和成核和生长动力学的spinode外的组合物。卡内基梅隆大学（CMU）的研究人员已经开发出了伪二元Fe 2 TiO 4-Fe 3 O 4系统中化合物的合成路线，可以更准确地定义该系统中的不对称可溶解性间隙。精细的微观结构导致的调幅分解和交换各向异性耦合机制可以解释一个大的缓慢衰减的reversible状态，这些矿物在火星上。富钛尖晶石的非饱和行为被假设为产生于非共线自旋。在调制的旋节结构的亚铁磁性磁铁矿的自旋耦合是感兴趣的。某些化合物更令人感兴趣，因为它们的磁性转变在火星上的昼夜温度范围内，因此可以用微型磁传感器检测到。该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。钛磁铁矿提供了一个丰富的磁性系统，探索精细的微观结构对磁性能的作用。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进行磁测绘比在地球上更强大。在地球上，地磁测量由于主磁场的存在而变得复杂，这使得地壳异常的测量具有挑战性且难以识别。全球磁测图的编制，结合对地壳和地表矿物及其还原状态的研究，可以为研究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传感器，该传感器基于CMU开发的磁膜，可以在火星表面的自然昼夜温度摆动中研究地外矿物的反磁性状态。这些传感器也可用于表征地球上的生物磁系统。拟议的研究涉及两个共享的博士生和本科生交流机制的发展。学生们还将参加在INTA举办的关于“火星及其谜”的INTA暑期学校。将提议在磁性和磁性材料会议上举行第二次“小型磁性传感器和传感器材料”卫星会议，以传播成果。

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.