Iron nitrides are possible constituents of the cores of Earth and other terrestrial planets. Pressure‐induced magnetic changes in iron nitrides and effects on compressibility remain poorly understood. Here we report synchrotron X‐ray emission spectroscopy (XES) and X‐ray diffraction (XRD) results for ε‐Fe₇N₃ and γ′‐Fe₄N up to 60 GPa at 300 K. The XES spectra reveal completion of high‐ to low‐spin transition in ε‐Fe₇N₃ and γ′‐Fe₄N at 43 and 34 GPa, respectively. The completion of the spin transition induces stiffening in bulk modulus of ε‐Fe₇N₃ by 22% at ~40 GPa, but has no resolvable effect on the compression behavior of γ′‐Fe₄N. Fitting pressure‐volume data to the Birch‐Murnaghan equation of state yields V₀ = 83.29 ± 0.03 (ų), K₀ = 232 ± 9 GPa, K₀′ = 4.1 ± 0.5 for nonmagnetic ε‐Fe₇N₃ above the spin transition completion pressure, and V₀ = 54.82 ± 0.02 (ų), K₀ = 152 ± 2 GPa, K₀′ = 4.0 ± 0.1 for γ′‐Fe₄N over the studied pressure range. By reexamining evidence for spin transition and effects on compressibility of other candidate components of terrestrial planet cores, Fe₃S, Fe₃P, Fe₇C₃, and Fe₃C based on previous XES and XRD measurements, we located the completion of high‐ to low‐spin transition at ~67, 38, 50, and 30 GPa at 300 K, respectively. The completion of spin transitions of Fe₃S, Fe₃P, and Fe₃C induces elastic stiffening, whereas that of Fe₇C₃ induces elastic softening. Changes in compressibility at completion of spin transitions in iron‐light element alloys may influence the properties of Earth's and planetary cores.

中文翻译：

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ε-Fe7N3和γ'-Fe4N的自旋转变和可压缩性：对地球行星铁芯中铁合金的影响

氮化铁可能是地球和其他陆地行星核心的组成部分。氮化铁中压力引起的磁性变化及其对可压缩性的影响仍然知之甚少。这里，我们报告同步辐射X射线发射光谱（XES）和X射线衍射（XRD）的结果为ε -铁₇ Ñ ₃和γ'-铁₄ Ñ高达60 GPA在300K的XES谱显示高的完成-在ε -铁低自旋过渡₇ ñ ₃和γ'-的Fe ₄ ñ在43和34 GPA，分别。自旋转移诱导的体积弹性模量的加强完成ε -铁₇ Ñ ₃通过在〜40 GPA 22％，但对γ'-Fe的压缩行为没有可分辨的效果₄ N.件压力-容积数据到状态产量的桦木-Murnaghan状态方程V ₀  = 83.29±0.03（ ³），ķ ₀  = 232±9 GPA，ķ ₀ '= 4.1±0.5对非磁性ε -铁₇ Ñ ₃自旋转移完成压力以上，并且V ₀  = 54.82±0.02（ ³），ķ ₀  = 152±2GPa的，ķ ₀ '= 4.0±为γ'-的Fe 0.1 ₄在所研究的压力区域N。通过重新审查自转转变以及对地球行星核心其他候选成分Fe ₃压缩性的影响的证据S，Fe ₃ P，Fe ₇ C ₃和Fe ₃ C基于先前的XES和XRD测量，我们确定了在300 K时〜67、38、50和30 GPa的高自旋转变完成。分别。Fe ₃ S，Fe ₃ P和Fe ₃ C的自旋转变完成会引起弹性硬化，而Fe ₇ C ₃的自旋转变会引起弹性软化。铁轻元素合金自旋转变完成时可压缩性的变化可能会影响地球和行星核的特性。