Magnetic properties of Fe-Ni and Fe-Si alloys under pressure: Confrontation of SQUID magnetometer and Mössbauer spectroscopy measurements

Fe-Ni 和 Fe-Si 合金在压力下的磁性：SQUID 磁力计与穆斯堡尔光谱测量的对比

• 批准号: 410243243
• 负责人: Dr. Qingguo Wei
• 金额: --
• 依托单位: Sektion Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/410243243?language=en
• 关键词: Magnetic; properties; Fe; Ni; Si

Iron together with nickel and light alloying elements such as silicon and sulfur, is believed to be the major constituent in cores of terrestrial planets. There is very little knowledge on magnetic properties of iron or materials in cores of terrestrial planets under high pressure. Such knowledge is important for understanding generation of magnetic field in planetary cores. Hexagonal closed packed (hcp) state is favored for Fe and Fe-Ni alloys in Earth’s inner core. By far, the magnetic state of hcp-Fe remains contentious. By confront superconducting quantum interference device (SQUID) magnetometer data with Mössbauer spectroscopy, we found that iron at 19.2 GPa still possessed a measurable remanent magnetization, whereas the sextets from hyperfine splitting in the Mössbauer spectra had completely disappeared. Understanding the origin behind the discrepancy between the SQUID magnetometer and Mössbauer spectroscopy results is of fundamental importance for anyone interested in magnetism, and especially those interested in high-pressure research. Fe68Ni32 and Fe64Ni36 are ferromagnetic at ambient condition with Curie temperatures of 128°C and 227°C, respectively. Their Curie points shift by about -45 K/GPa and -35 K/GPa, which means above ~3 GPa and ~6 GPa they should become paramagnetic. In our experiments, a measurable ferromagnetic remanent magnetization persists in Fe64Ni36 up to 16.3 GPa and becomes much more magnetic immediately upon decompression. We would like to confirm this on Fe68Ni32 and confront both Fe68Ni32 and Fe64Ni36 against Mössbauer. In our experiments, we also found that SIRM and sextet peak intensities correlated well under pressures. The mechanism for this is unclear. It is important to verify whether such a relationship is repeatable on other samples. Bcc-Fe91Si09 is a good candidate. It is ferromagnetic at ambient conditions. With Si alloyed in Fe, bcc Fe91Si09 is stable up to 50 GPa at room temperature. Importantly, our preliminary work suggests that the SIRM of Fe91Si09 constantly increases with compression up to 20 GPa and further still upon decompression. Here, we propose a further study on magnetization of Fe-Ni alloys around invar range (Fe68Ni32 and Fe64Ni36) and Fe-Si alloy (Fe91Si09) under high pressures: continue confrontation SQUID magnetometer and Mössbasuer spectroscopy in one non-magnetic diamond anvil cell.

铁与镍和轻合金元素如硅和硫一起被认为是类地行星核心的主要成分。关于铁或类地行星内核中的物质在高压下的磁性，人们知之甚少。这些知识对于理解行星核心磁场的产生非常重要。在地球内核中，铁和铁镍合金倾向于以六方密堆积（hcp）状态存在。到目前为止，hcp-Fe的磁性状态仍然存在争议。将超导量子干涉仪（SQUID）的磁强计数据与穆斯堡尔谱进行对比，我们发现铁在19.2 GPa下仍然具有可测量的回复磁化，而穆斯堡尔谱中超精细分裂的六位体已经完全消失。了解SQUID磁强计和穆斯堡尔谱结果之间差异的根源对于任何对磁性感兴趣的人，特别是那些对高压研究感兴趣的人来说都非常重要。Fe 68 Ni 32和Fe 64 Ni 36在环境条件下是铁磁性的，居里温度分别为128°C和227°C。它们的居里点移动了约-45 K/GPa和-35 K/GPa，这意味着在~3 GPa和~6 GPa以上，它们应该成为顺磁性的。在我们的实验中，一个可测量的铁磁reximation磁化持续在Fe 64 Ni 36高达16.3 GPa，并成为更多的磁性立即减压。我们想在Fe 68 Ni 32上证实这一点，并与Fe 68 Ni 32和Fe 64 Ni 36对抗穆斯堡尔。在我们的实验中，我们还发现，SIRM和六重峰强度相关的压力下。其机制尚不清楚。重要的是要验证这种关系是否可以在其他样品上重复。Bcc-Fe_（91）Si_（09）是一个很好的候选者。在环境条件下具有铁磁性。在Fe中合金化Si的情况下，bcc Fe 91 Si 09在室温下高达50 GPa是稳定的。重要的是，我们的初步工作表明，Fe 91 SiO 9的SIRM随着压缩到20 GPa而不断增加，并且在减压时进一步增加。在此，我们提出了在高压下对Fe-Ni合金（Fe 68 Ni 32和Fe 64 Ni 36）和Fe-Si合金（Fe 91 Si 09）的磁化强度进行进一步的研究：在一个非磁性金刚石对顶砧单元中继续对抗SQUID磁强计和Mössbasuer光谱。