Hysteresis and stepwise structure in MR curves of granular superconducting ruthenocuprates RuSr$_2$(Gd$_{1.5}$Ce$_{0.5})$Cu$_2$O$_{10-\delta}$}

TL;DR

This study investigates the magnetic and resistive behaviors of granular ruthenocuprate superconductors, revealing hysteresis types, crossing point effects, and stepwise MR structures linked to inhomogeneous intergrain states.

Contribution

It provides new insights into the hysteresis phenomena and stepwise MR structures in granular superconductors, emphasizing the role of inhomogeneity and temperature effects.

Findings

Identification of clockwise and anticlockwise hysteresis in MR curves

Observation of crossing point effect in differential resistance

Detection of stepwise structures in low-field MR hysteresis

Abstract

Granular superconductivity effects in a polycrystalline sample of ruthenocuprate RuSr$_2$(Gd$_{1.5}$Ce$_{0.5})$Cu$_2$O$_{10-\delta}$ are studied. The main attention has been devoted to manifestation of these effects in current and magnetic-field dependences of resistive transition to superconducting state. It is found that current dependences of differential resistance taken at different temperatures intersect strictly at two definite values of current demonstrating crossing point effect. This phenomenon has been explained taking into account inhomogeneous state of intergrain medium which can be considered as a two-component system. The particular attention has been given to magnetoresistance (MR) hysteresis in mixed state of this inhomogeneous system and to influence of applied current and temperature on this phenomenon. Two types of hysteresis (clockwise and anticlockwise) have been found with transition from clockwise to anticlockwise hysteresis with increasing temperature. Stepwise structure in MR hysteretic curves has been observed in low-field range. Possible reasons of the change in hysteresis behavior with increasing temperature and appearance of the stepwise structure in MR curves are discussed taking into consideration inhomogeneous state of the granular superconductor studied.