Structure and magnetism of the solid solution GexFe4−xNy (0 ≤ x ≤ 1): from a ferromagnet to a spin glass
Structure and magnetism of the solid solution GexFe4−xNy (0 ≤ x ≤ 1): from a ferromagnet to a spin glass
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DOI：
10.1039/c6tc04543j
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发表时间：
2017
影响因子：
6.4
通讯作者：
T. Scholz;R. Dronskowski
中科院分区：
文献类型：
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作者：
T. Scholz;R. Dronskowski
本文对固溶体GexFe4−xNy（0≤x≤1）进行了实验和理论研究。两步氨解反应可获得相纯质量的化合物。随着锗浓度的增加，GexFe4−xNy氮化物呈现出由反钙钛矿样结构向四方扭曲结构的转变。各种实验和理论方法证明，锗取代铁只发生在立方Wyckoff位置1a。尽管存在相变，但在整个组成范围内，晶格参数呈维加德型减小。此外，氮化物具有有限的氮容量：加入锗大大降低了立方结构中的氮含量，但在四方结构中又增加了氮含量。结合HT-XRD和TG-DSC测量，证明富锗氮化物是高膨胀材料。它们首先表现出向立方结构的转变，然后通过释放氮来分解。磁性测量表明，锗的逐渐掺入伴随着铁磁相互作用的急剧减弱，导致铁自旋系统受挫。Ge0.97Fe3.03N0.56为典型自旋玻璃，其特征参数为Tg = 36.68(5) K, τ* = 10−13.8(2)s, zν = 7.2(1)， ΔTm/(Tm·Δ lg ω) = 0.012。
We present an experimental and theoretical study of the solid solution GexFe4−xNy (0 ≤ x ≤ 1). A two-step ammonolytic reaction gives access to the compounds with phase-pure quality. The GexFe4−xNy nitrides show a transition from an antiperovskite-like to a tetragonally distorted structure with increasing germanium concentration. Various experimental and theoretical methods evidence that the iron substitution by germanium exclusively takes place at the cubic Wyckoff position 1a. Despite the phase transition, one observes a Vegard-type decrease of the lattice parameter over the entire compositional range. In addition, the nitrides have a limited nitrogen capacity: incorporating germanium drastically reduces the nitrogen content in the cubic structure, but increases it again in the tetragonal structure. Combined HT-XRD and TG-DSC measurements evidence that the germanium-richest nitrides are highly expanding materials. They first show a transition to a cubic structure before they decompose by releasing nitrogen. Magnetic measurements reveal that the gradual germanium incorporation is accompanied by a drastic weakening of the ferromagnetic interactions leading to a frustrated iron spin system. Ge0.97Fe3.03N0.56 is identified as a canonical spin glass with the characteristic parameters Tg = 36.68(5) K, τ* = 10−13.8(2) s, zν = 7.2(1) and ΔTm/(Tm·Δ lg ω) = 0.012.