Structural and superconducting properties of RbOs2O6 single crystals

Abstract

Single crystals of RbOs2O6 have been grown from Rb2O and Os in sealed quartz ampoules. The crystal structure has been identified at room temperature as cubic with the lattice constant a=10.1242(12)Å. The anisotropy of the tetrahedral and octahedral networks is lower and the displacement parameters of alkali metal atoms are smaller than those for KOs2O6, so the “rattling” of the alkali atoms in RbOs2O6 is less pronounced. The superconducting properties of RbOs2O6 in the mixed state have been described well within the London approach and the Ginzburg–Landau parameter κ(0)≅31 has been derived from the reversible magnetization. This parameter is field dependent and changes at low temperatures from κ≅22 (low fields) to κ≅31 at Hc2. The thermodynamic critical field Hc(0)=1.3kOe and the superconducting gap 2Δo∕kBTc≅3.2 have been estimated. These results, together with the slightly different Hc2(T) dependence obtained for crystals and polycrystalline RbOs2O6, evidently prove that this compound is a weak-coupling BCS-type superconductor close to the dirty limit.

Source-reported materials — not catalogue approval

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