Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA.
J Am Chem Soc. 2009 Mar 11;131(9):3349-54. doi: 10.1021/ja809084n.
Metal flux synthesis in a low-melting eutectic mixture of lanthanum and nickel has produced a family of complex intermetallic carbide phases. La(21)Fe(8)M(7)C(12) (M = Sn, Bi, Sb, Te, Ge) has a new cubic structure featuring tetrahedra of iron atoms capped with carbon on each edge. These tetrahedra are surrounded by a La/M framework and are therefore isolated from each other. The antiferromagnetic coupling of the iron atoms is frustrated by their ideal tetrahedral arrangement; this is evidenced by magnetic susceptibility measurements on the La(21)Fe(8)Sn(7)C(12) analogue. Deviations from Curie-Weiss behavior begin at 100 K; variation in field-cooled vs zero-field-cooled behavior is seen at 5 K indicative of magnetic ordering. AC susceptibility data indicate that the temperature of this transition is frequency-dependent, behavior characteristic of spin glass systems.
金属在镧镍低共熔混合物中的通量合成产生了一系列复杂的金属间碳化物相。La(21)Fe(8)M(7)C(12)（M = Sn、Bi、Sb、Te、Ge）具有一种新的立方结构，其特征是每个边缘都用碳覆盖的铁原子四面体。这些四面体被 La/M 框架包围，因此彼此隔离。铁原子的反铁磁耦合由于其理想的四面体排列而受到阻碍；这可以通过对 La(21)Fe(8)Sn(7)C(12)类似物的磁化率测量来证明。偏离居里-外斯行为始于 100 K；在 5 K 时观察到磁场冷却与零场冷却行为的变化，表明存在磁有序。交流磁化率数据表明，这种转变的温度与频率有关，这是自旋玻璃系统的特征行为。
