Zhou Sixuan, Mishra Trinath, Wang Man, Shatruk Michael, Cao Huibo, Latturner Susan E
Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States.
Inorg Chem. 2014 Jun 16;53(12):6141-8. doi: 10.1021/ic5005984. Epub 2014 Jun 5.
The intermetallic compounds R2Co2SiC (R = Pr, Nd) were prepared from the reaction of silicon and carbon in either Pr/Co or Nd/Co eutectic flux. These phases crystallize with a new stuffed variant of the W2CoB2 structure type in orthorhombic space group Immm with unit cell parameters a = 3.978(4) Å, b = 6.094(5) Å, c = 8.903(8) Å (Z = 2; R1 = 0.0302) for Nd2Co2SiC. Silicon, cobalt, and carbon atoms form two-dimensional flat sheets, which are separated by puckered layers of rare-earth cations. Magnetic susceptibility measurements indicate that the rare earth cations in both analogues order ferromagnetically at low temperature (TC ≈ 12 K for Nd2Co2SiC and TC ≈ 20 K for Pr2Co2SiC). Single-crystal neutron diffraction data for Nd2Co2SiC indicate that Nd moments initially align ferromagnetically along the c axis around ∼12 K, but below 11 K, they tilt slightly away from the c axis, in the ac plane. Electronic structure calculations confirm the lack of spin polarization for Co 3d moments.
金属间化合物R2Co2SiC（R = Pr，Nd）是通过硅和碳在Pr/Co或Nd/Co共熔剂中反应制备的。这些相在正交空间群Immm中以W2CoB2结构类型的一种新的填充变体结晶，对于Nd2Co2SiC，其晶胞参数为a = 3.978(4) Å，b = 6.094(5) Å，c = 8.903(8) Å（Z = 2；R1 = 0.0302）。硅、钴和碳原子形成二维平面，这些平面被稀土阳离子的褶皱层隔开。磁化率测量表明，两种类似物中的稀土阳离子在低温下呈铁磁有序（Nd2Co2SiC的居里温度TC≈12 K，Pr2Co2SiC的居里温度TC≈20 K）。Nd2Co2SiC的单晶中子衍射数据表明，Nd磁矩最初在约12 K时沿c轴呈铁磁排列，但在11 K以下，它们在ac平面中略微偏离c轴倾斜。电子结构计算证实Co 3d磁矩缺乏自旋极化。
