100 research outputs found
The Effect of Ru substitution for Ni on the superconductivity in MgCNi3-xRux
The superconductor MgCNi3 has been chemically doped by partial substitution
of Ru for Ni in the solid solution MgCNi3-xRux for 0<x<0.5. Magnetic and
specific heat measurements show that the Sommerfeld parameter (gamma_exp) and
TC decrease immediately on Ru substitution, but that a TC above 2K is
maintained even for a relatively large decrease in gamma_exp. Ferromagnetism is
not observed to develop through Ru substitution, and the normal state magnetic
susceptibility is suppressed.Comment: 18 pages, 13 figure
Superconductivity in Mg10Ir19B16
Mg10Ir19B16, a previously unreported compound in the Mg-Ir-B chemical system,
is found to be superconducting at temperatures near 5 K. The fact that the
compound exhibits a range of superconducting temperatures between 4 and 5 K
suggests that a range of stoichiometries is allowed, though no structural
evidence for this is observed. The compound has a large, noncentrosymmetric,
body centered cubic unit cell with a = 10.568 Angstrom, displaying a structure
type for which no previous superconductors have been reported.Comment: submitted to PR
Muon spin rotation/relaxation measurements of the non-centrosymmetric superconductor Mg10Ir19B16
We have searched for time-reversal symmetry breaking fields in the
non-centrosymmetric superconductor MgIrB via muon spin
relaxation in zero applied field, and we measured the temperature dependence of
the superfluid density by muon spin rotation in transverse field to investigate
the superconducting pairing symmetry in two polycrystalline samples of
signficantly different purities. In the high purity sample, we detected no
time-reversal symmetry breaking fields greater than 0.05 G. The superfluid
density was also found to be exponentially-flat as T0, and so can be fit
to a single-gap BCS model. In contrast, the lower purity sample showed an
increase in the zero-field SR relaxation rate below T corresponding to
a characteristic field strength of 0.6 G. While the temperature-dependence of
the superfluid density was also found to be consistent with a single-gap BCS
model, the magnitude as T0 was found to be much lower for a given applied
field than in the case of the high purity sample. These findings suggest that
the dominant pairing symmetry in high quality MgIrB
samples corresponds to the spin-singlet channel, while sample quality
drastically affects the superconducting properties of this system.Comment: 6 pages, 5 figures, revised version resubmitted to PR
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