Superconductivity of MI(MII0.5,Si0.5)2 (MI=Sr and Ba, MII=Al and Ga), ternary silicides with the AlB2-type structure

Abstract

Ternary silicides M I (M II0.5 , Si 0.5 ) 2 (M I =Sr and Ba, M II =Al and Ga) were prepared by Ar arc melting. Powder X-ray diffraction indicates that they have the AlB 2 -type structure, in which Si and M II atoms are arranged in honeycomb layers and M I atoms are intercalated between them. Electrical resistivity and dc magnetization measurements revealed that Sr(Al 0.5 , Si 0.5 ) 2 is superconductive, with a critical temperature for superconductivity (T C ) of 4.2 K, while Ba(Al 0.5 , Si 0.5 ) 2 is not at temperatures ranging above 2.0 K. Sr(Ga 0.5 , Si 0.5 ) 2 and Ba(Ga 0.5 , Si 0.5 ) 2 are also superconductors, with T C s of 5.1 and 3.3 K, respectively.

Synthesis of Sr0.99Eu0.01AlSiN3 from intermetallic precursor

“…1), the intermetallic precursor was near single phase, having AlB2-type structure as previous report 17) with trace amount of SrAl2Si2 phase. After the milling, the oxygen content was below 0.3 wt%.…”

Electronic structure of YbGa1.15Si0.85and YbGaYamaoka1, Jarrige2, Tsujii3 et al. 2011Phys. Rev. BSelf Cite

“…Ternary silicides with the AlB 2 -type structure also showed superconductivity. [4][5][6][7][8] The superconductivity was also related to the lattice parameter within the layer rather than the interlayer spacing as shown in M AlSi (M =Ca, Sr, Ba). 9 Inelastic x-ray scattering for CaAlSi suggested soft-phonon-driven superconductivity, i. e. a conventional BCS superconductor in weak coupling regime.…”

Comparison of physical properties in BaAlSi and CaAlSi

“…Since it is expected that the Debye temperatures in these compounds are similar, SrAlSi and BaAlSi should also show superconductivity with T c comparable to CaAlSi. However, T c of SrAlSi is reported to be 4.2 K, lower than that of CaAlSi, and BaAlSi does not even show superconductivity at temperature down to 2 K [2].…”

“…Since the discovery of MgB 2 [1], a lot of superconductors with AlB 2 structure have been developed [2][3][4][5][6]. Among them, CaAlSi is a superconductor with a relatively high superconducting transition temperature T c of 7.7 K [7].…”

“…Several anomalous properties are reported in CaAlSi, such as the anomalous positive pressure dependence of the transition temperature [8], and the anomalous angular dependence of the upper critical field [9]. Replacements of Ca in CaAlSi by other alkaline earth elements also result in the compounds with AlB 2 structure, such as SrAlSi and BaAlSi [2]. Band structure calculations show that the density of states in BaAlSi and SrAlSi is higher than that of CaAlSi [8].…”