Susceptibility and X-ray absorption measurements on superconducting (Hg,Mo)Sr2CuO4+delta system

Abstract

In continuation of our recent work [1] on superconducting 1201-type (Hg,M)Sr2CuO4+delta M = Cr system, the samples of (Hg1-xMx)Sr2CuO4+delta, M = Mo (x = 0.15, 0.25, and 0.30), were synthesised in partial vacuum. The x = 0.15 composition shows a maximum T-c(onset) of similar to 66 K. while x = 0.25 exhibits T-c(onset) of -50 K. For x = 0.30 sample, the observed T-c(onset) of discretely different from the reported values of 20 and 58 K. X-ray absorption measurements on (Hg,Mo)-1201 samples show Hg in divalent state and Cu predominantly in Cu2+ state. A weak but distinct Cu1+ signature is also observed in the SC (Hg,Mo)-1201 samples., which is absent in the impurity SrCuO2 and Sr2CuO3 phases. On the basis of available reports, it is viewed that Cu1+ can arise because of a small fraction of Cu occupying the Hg site in (Hg,Mo)-1201 system.