Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
J Am Chem Soc. 2017 Mar 22;139(11):4130-4143. doi: 10.1021/jacs.7b00284. Epub 2017 Mar 8.
A new polymorph of the RERuGe (RE = Pr, Sm, Dy) compounds has been grown as single crystals via an indium flux. These compounds crystallize in tetragonal space group P4/mnc with the ScFeSi-type structure, having lattice parameters a = 11.020(2) Å and c = 5.853(1) Å for RE = Pr, a = 10.982(2) Å and c = 5.777(1) Å for RE = Sm, and a = 10.927(2) Å and c = 5.697(1) Å for RE = Dy. These materials exhibit a structural transition at low temperature, which is attributed to an apparent charge density wave (CDW). Both the high-temperature average crystal structure and the low-temperature incommensurately modulated crystal structure (for SmRuGe as a representative) have been solved. The charge density wave order is manifested by periodic distortions of the one-dimensional zigzag Ge chains. From X-ray diffraction, charge transport (electrical resistivity, Hall effect, magnetoresistance), magnetic measurements, and heat capacity, the ordering temperatures (T) observed in the Pr and Sm analogues are ∼200 and ∼175 K, respectively. The charge transport measurement results indicate an electronic state transition happening simultaneously with the CDW transition. X-ray absorption near-edge spectroscopy (XANES) and electronic band structure results are also reported.
一种新的 RERuGe（RE = Pr、Sm、Dy）化合物多晶型物已通过铟流成功生长为单晶。这些化合物属于四方晶系 P4/mnc，具有 ScFeSi 型结构，晶格参数分别为 a = 11.020(2) Å 和 c = 5.853(1) Å（RE = Pr）、a = 10.982(2) Å 和 c = 5.777(1) Å（RE = Sm）以及 a = 10.927(2) Å 和 c = 5.697(1) Å（RE = Dy）。这些材料在低温下表现出结构相变，这归因于明显的电荷密度波（CDW）。已经解决了高温平均晶体结构和低温非共调调制晶体结构（以 SmRuGe 为例）。电荷密度波有序表现为一维之字形 Ge 链的周期性畸变。从 X 射线衍射、电荷输运（电阻率、霍尔效应、磁阻）、磁测量和热容来看，在 Pr 和 Sm 类似物中观察到的有序温度（T）分别约为 200 和 175 K。电荷输运测量结果表明，电子态跃迁与 CDW 跃迁同时发生。还报告了 X 射线吸收近边光谱（XANES）和电子能带结构结果。
