IMPACT OF Co AND Mo SUBSTITUTION AT Ru-SITE IN RuSr2Eu1.5Ce0.5Cu2O10-δ MAGNETO-SUPERCONDUCTOR

Substitution of both Co and Mo at Ru -site in RuSr 2 Eu 1.5 Ce 0.5 Cu 2 O 10-δ system takes place iso-structurally in tetragonal structure (space group I4/mmm) with full solubility. The resistance versus temperature (R versus T) behavior of the pristine sample confirmed superconductivity [Formula: see text] around 25 K. The DC magnetization data (M versus T) for the same sample revealed magnetic transition (T mag ) at 140 K followed by superconducting transition [Formula: see text] at 32 K. With progressive Co substitution at Ru -site both [Formula: see text] and [Formula: see text] decrease monotonically and superconductivity is not observed for x ≥ 0.10 (10 at%). The magnetic behavior of materials with Co up to x = 0.2 preserves the magnetic structure of the parent RuSr 2 Eu 1.5 Ce 0.5 Cu 2 O 10-δ compound. For 0.8 ≥ x ≥ 0.2 a clear antiferromagnetic transition at TN=31 K is observed regardless of Co content. In the case of Mo -doped ruthenocuprates Ru 1-x Mo x Sr 2 Eu 1.5 Ce 0.5 Cu 2 O 10-δ, it has been found that the magnetic transition temperature decreases with x. The samples of x = 0.8 and 1.0 are found to have no magnetic or superconducting effects. The values of the superconducting transition temperature obtained from the resistivity versus temperature data increase by 4.5 and 7.0 K for x = 0.2 and 0.4 respectively, and then decrease by 17 K for x = 0.6. The observed variation of Tc with x in case of Mo has been explained in terms of a theory which combines the effects of weakening magnetic behavior and reducing carrier concentration in a phenomenological manner.