Discovery of Spin Glass Behavior in Ln2Fe4Sb5 (Ln = La–Nd and Sm)

Single crystals of Ln2Fe4Sb5 (Ln = La–Nd and Sm) were grown from an inert Bi flux. Measurements of the single crystal X-ray diffraction revealed that these compounds crystallize in the tetragonal space group I4/mmm with lattice parameters of a ≈ 4 Å, c ≈ 26 Å, V ≈ 500 Å3, and Z = 2. This crystal structure consists of alternating LnSb8 square antiprisms and Fe-sublattices composed of nearly equilateral triangles of bonded Fe atoms. These compounds are metallic and display spin glass behavior, which originates from the magnetic interactions within the Fe-sublattice. Specific heat measurements are void of any sharp features that can be interpreted as contributions from phase transitions as is typical for spin glass systems. A large, approximately linear in temperature, contribution to the specific heat of La2Fe4Sb5 is observed at low temperatures that we interpret as having a magnetic origin. Herein, we report the synthesis, structure, and physical properties of Ln2Fe4Sb5 (Ln = La–Nd and Sm).

Ln₂Fe₄Sb₅（Ln = La–Nd 及 Sm）单晶通过惰性铋（Bi）助熔剂法制备得到。经单晶X射线衍射（single crystal X-ray diffraction）表征证实，该系列化合物结晶于四方晶系空间群I4/mmm，晶格参数分别为a≈4 Å、c≈26 Å，晶胞体积V≈500 ų，晶胞内化学式单元数Z=2。其晶体结构由交替排列的LnSb₈方形反棱柱与由近乎等边键合铁原子构成的三角形铁亚晶格组成。该类化合物呈金属性，并表现出自旋玻璃行为，该行为起源于铁亚晶格内的磁相互作用。比热容测试未观测到可归因于相变的尖锐特征，这与自旋玻璃体系的典型特性相符。在低温条件下，La₂Fe₄Sb₅的比热容呈现出显著的、近似随温度线性变化的贡献，我们判定该贡献源自磁性起源。本文报道了Ln₂Fe₄Sb₅（Ln = La–Nd 及 Sm）的合成方法、晶体结构与物理性能。