铁砷氟化物SrFeAsF的合成、晶体结构及自旋密度波异常
Synthesis, crystal structure and spin-density-wave anomaly of the iron arsenide-fluoride SrFeAsF
摘要：
合成了四元ZrCuSiAs型结构的四元铁砷氟化物SrFeAsF，用X射线粉末衍射法测定了其晶体结构（P4/nmm，a = 399.30（1），c = 895.46（1）pm）。SrFeAsF在175 K发生结构和磁性相变，并伴随着比热、电阻和磁化率的强烈异常。在这个转变过程中，空间群对称性从四方晶系（P4/nmm）转变为正交晶系（Cmme）。~（57）Fe穆斯堡尔谱实验表明，在室温下，同质异能素位移为0.30（1）mm/s，磁超精细场分裂在低于相变温度时出现。我们的研究结果清楚地表明，SrFeAsF表现出自旋密度波（SDW）异常在175 K非常相似的砷化铁氧化物超导体的母体化合物LaFeAsO，因此SrFeAsF可以作为进一步的母体化合物的无氧砷化铁超导体。
英文摘要：
The new quaternary iron arsenide-fluoride SrFeAsF with the tetragonal ZrCuSiAs-type structure was synthesized and the crystal structure was determined by X-ray powder diffraction (P4/nmm, a = 399.30(1), c = 895.46(1) pm). SrFeAsF undergoes a structural and magnetic phase transition at 175 K, accompanied by strong anomalies in the specific heat, electrical resistance and magnetic susceptibility. In the course of this transition, the space group symmetry changes from tetragonal (P4/nmm) to orthorhombic (Cmme). 57Fe Moessbauer spectroscopy experiments show a single signal at room temperature at an isomer shift of 0.30(1) mm/s and magnetic hyperfine-field splitting below the phase transition temperature. Our results clearly show that SrFeAsF exhibits a spin density wave (SDW) anomaly at 175 K very similar to LaFeAsO, the parent compound of the iron arsenide-oxide superconductors and thus SrFeAsF may serve as a further parent compound for oxygen-free iron arsenide superconductors.
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