I-V curves and intergranular flux creep activation energy in the magnetic superconductor RuSr2GdCu2O8

TL;DR

This study investigates the flux creep activation energy and I-V characteristics of the magnetic superconductor RuSr2GdCu2O8, revealing how magnetic fields and temperature influence flux pinning and intergranular behavior.

Contribution

It provides the first detailed analysis of flux creep activation energy in RuSr2GdCu2O8, highlighting its dependence on magnetic field and temperature, and compares it with non-magnetic cuprates.

Findings

Activation energy E_a(H,T) varies linearly with temperature.

E_a(H,T) shows a power-law dependence on magnetic field up to 0.1 T.

Critical current density J_C(0,0) is about ten times lower than in YBa2Cu3O7.

Abstract

A systematic study of I-V characteristic curves for RuSr2GdCu2O8 [Ru-(1212)] is presented, with magnetic fields up to 3 T and 5 K<T<30 K, in the region of the superconducting transition. The activation energy E_{a}(H,T) for flux line depinning was determined by fitting the nonlinear region of the curves using the flux creep model. E_{a}(H,T) was found to vary linearly with temperature, while a power-law dependence on the magnetic field was observed up to H=0.1 T, where an abrupt reduction in its decreasing rate occurs. The extrapolated value, E_{a}(0,0)=50 meV, is twice the reported value for YBa2Cu3O7, but the critical current density J_{C}(0,0)=70 A/cm2 is about one order of magnitude lower. These results are explained as a consequence of the contribution of the magnetization in the grains to the effective field at the intergranular links and to a spin-flop transition of the Ru-sub-lattice.