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Title: Effect of Eu substitution on superconductivity in Ba{sub 8−x}Eu{sub x}Al{sub 6}Si{sub 40} clathrates

The silicon clathrate superconductor is uncommon as its structure is dominated by strong Si-Si covalent bonds, rather than the metallic bond, that are more typical of traditional superconductors. To understand the influence of large magnetic moment of Eu on superconductivity for type-I clathrates, a series of samples with the chemical formula Ba{sub 8−x}Eu{sub x}Al{sub 6}Si{sub 40} (x = 0, 0.5, 1, and 2) were synthesised in which Eu occupied Ba sites in cage center. With the increase of Eu content, the cubic lattice parameter decreases monotonically signifying continuous shrinkage of the constituting (Ba/Eu)@Si{sub 20} and (Ba/Eu)@Si{sub 24} cages. The temperature dependence of magnetization at low temperature revealed that Ba{sub 8}Al{sub 6}Si{sub 40} is superconductive with transition temperature at T{sub C} = 5.6 K. The substitution of Eu for Ba results in a strong superconductivity suppression; Eu-doping largely decreases the superconducting volume and transition temperature T{sub C}. Eu atoms enter the clathrate lattice and their magnetic moments break paired electrons. The Curie-Weiss temperatures were observed at 3.9, 6.6, and 10.9 K, respectively, for samples with x = 0.5, 1.0, and 2.0. Such ferromagnetic interaction of Eu can destroy superconductivity.
Authors:
; ;  [1] ;  [2]
  1. Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China)
  2. Department of Engineering Science and Materials, University of Puerto Rico at Mayaguez, Mayaguez, Puerto Rico 00681-9044 (United States)
Publication Date:
OSTI Identifier:
22410132
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM SILICATES; BARIUM COMPOUNDS; CHEMICAL BONDS; CLATHRATES; CONCENTRATION RATIO; CUBIC LATTICES; ELECTRONS; EUROPIUM COMPOUNDS; MAGNETIC MOMENTS; MAGNETIZATION; SILICON; SUPERCONDUCTIVITY; SUPERCONDUCTORS; SYNTHESIS; TEMPERATURE DEPENDENCE; TRANSITION TEMPERATURE