Structural analysis, magnetic and transport properties of the (Ru1-xCox)Sr2GdCu2O8 system

TL;DR

This study investigates how cobalt substitution affects the structure, magnetism, and superconductivity of RuSr2GdCu2O8, revealing structural stability but significant magnetic and superconducting property changes with increasing Co content.

Contribution

It provides detailed insights into the structural and magnetic effects of Co doping in RuSr2GdCu2O8, including bond angle stability and magnetic moment variations, which were not previously characterized.

Findings

Co substitution replaces Ru sites progressively.

Weak ferromagnetic transition shifts to lower temperature with Co.

Increasing Co enhances weak ferromagnetic moment.

Abstract

The effects of Co substitution on structural and superconducting properties of RuSr2GdCu2O8 compound have been studied. Rietveld refinements of the X-ray diffraction patterns indicate that the cobalt ion progressively replaces ruthenium sites. This replacement induces significant changes on the crystal structure and on the magnetic and superconducting properties. The effects Co substitution on the superconducting behaviour, and more particulary on the changes induce by the hole doping mechanism, were investigated in (Ru1-xCox)Sr2GdCu2O8 by a "bond valence sum" analysis with Co content from x= 0.0 to x = 0.2. The weak ferromagnetic transition at Tm= 138.2 K is shifted to lower temperature, and suppressed at higher Co content. From the crystallographic point of view the Ru-O(1)-Cu bond angle, associated to the rotation of the RuO6 octahedra, around the c-axis remain essetially constant when Ru is substituted by Co. Furthermore, increasing Co content has the effect to increase the weak ferromagnetic moment, which may be interpreted as the main responsible for breaking the delicate balance between magnetic and superconducting ordering.