Tuning the superconducting state in the magnetic MoSr2YCu2O8 materials

The properties of the MoSr2YCu2O8 materials are found to systematically change with the oxygen concentration determined by the sintering and annealing conditions. The as-prepared (asp) sample is anti-ferromagnetically (AFM) ordered at 16 K. The magnetic features are related to the Mo5+ sublattice. Annealing under an oxygen atmosphere induces superconductivity (SC) in the Cu-O planes, and the TC and the shielding fraction values obtained depend strongly on the oxygen concentration. Annealing the asp material at 1030 C under ambient oxygen atmosphere yields TC of 18 K, whereas further annealing at 650 C under 92 atm. of oxygen, shifts TC to 32 K. The AFM ordering, which coexists with SC state through effectively decoupled subsystems, is not affected by the presence or absence of the SC state. In all samples studied, TN < TC. This behavior resembles most of the inter-metallic magneto-superconductors, but is in sharp contrast to the iso-structural RuSr2GdCu2O8 system where TN > TC.Comment: 7 pages, 8 Figure

The magnetic behavior of Li2MO3 (M=Mn, Ru and Ir) and Li2(Mn1-xRux)O3

The present study summerizes magnetic and Mossbauer measurements on ceramic Li2MO3 M= Mn, Ru and Ir and the mixed Li2(Mn1-xRux)O3 materials, which show many of the features reflecting to antiferromagnetic ordering or to existence of paramagnetic states. Li2IrO3 and Li2RuO3 are paramagnetic down to 5 K. Li2(Mn1-xRux)O3 compounds are antiferromagnetically ordered at TN = 48 K for x=0. TN decreases as the Ru content increases and, for x=0.8, TN =34 K.Comment: accepted to Physica