Verchenko Valeriy Yu, Zubtsovskii Alexander O, Wei Zheng, Tsirlin Alexander A, Dikarev Evgeny V, Shevelkov Andrei V
Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia.
Dalton Trans. 2019 Jun 14;48(22):7853-7861. doi: 10.1039/c8dt04982c. Epub 2019 May 10.
Using the crystal-growth joint flux technique based on the combination of two aliovalent low-melt metals, gallium and zinc, we adjust the gross valence electron count in the Mo-Ga-Zn system and produce the MoGaZn and MoGaZn intermetallic compounds. Gradual reduction in the valence electron count first leads to the Zn for Ga substitution in the MoGa endohedral cluster superconductor, accompanied by the formation of Zn-containing clusters in the crystal structure and by the gradual suppression of superconductivity. MoGaZn with x = 7.2(2) exhibits superconducting properties below T = 4 K, whereas there is no superconducting transition at temperatures above 2 K for the limiting composition of x = 11.3(2). Further, the MoGaZn phase is formed from the flux with a higher content of Zn. MoGaZn crystallizes in the MoSnZn structure type with a narrow homogeneity range and exhibits metallic behavior with no sign of superconductivity down to at least 1.8 K. Its experimental valence electron count of 2.9 e per atom is below that of endohedral gallium cluster superconductors. Electronic structures of MoGaZn and MoGaZn feature the opening of a pseudogap slightly below the Fermi level indicating the specific stability of these structure types at the valence electron count of 3.2 e per atom and 2.7 e per atom, respectively.
利用基于两种异价低熔点金属镓和锌组合的晶体生长联合助熔剂技术，我们在Mo - Ga - Zn体系中调整总价电子数，并制备出MoGaZn和MoGaZn金属间化合物。价电子数的逐渐减少首先导致在MoGa内包簇超导体中锌取代镓，同时在晶体结构中形成含锌簇，并逐渐抑制超导性。x = 7.2(2)的MoGaZn在T = 4 K以下表现出超导性能，而对于极限组成x = 11.3(2)，在2 K以上的温度没有超导转变。此外，MoGaZn相由锌含量更高的助熔剂形成。MoGaZn以MoSnZn结构类型结晶，均匀性范围狭窄，并且在至少1.8 K以下表现出金属行为，没有超导迹象。其每个原子的实验价电子数为2.9 e，低于内包镓簇超导体。MoGaZn和MoGaZn的电子结构在略低于费米能级处出现赝能隙，分别表明这些结构类型在每个原子3.2 e和2.7 e的价电子数下具有特定稳定性。
